My main problem with the film as it currently is isn't so much the characters in it or the messages being presented, it's with the execution itself. IMHO, there are far too many scenes in the film that either don't give us enough context or build-up for a later scene to work, or which create 'Fridge Logic' moments, as TVTropes would put it. To fix these, I'd make the following changes - OBVIOUS SPOILERS INBOUND:
*Add an extended opening montage sequence actually showing the fall of the New Republic. The distinction between the New Republic and the Resistance is something that has only been properly explained in tie-in material - to elaborate, the Resistance is a private military group founded by Leia Organa in a time when the New Republic was pursuing a disarmament policy - and so it can come off as strange to a viewer that the loss of a single planet in the Force Awakens automatically leads to the First Order successfully taking over the entire galaxy and the Resistance being reduced to a very small group when very little time has passed between the end of the last film and the start of this one.
So, to fix this, I'd have the film starting with several short scenes where First Order vessels are shown advancing on planets, fighting on the surface and overwhelming local militias - a la The Phantom Menace - and so on. It'd only need to be about as long as the "Execute Order 66" scene from Revenge of the Sith, and show just as many different planets. Anyway, as the montage ends, we'd see the militias surrendering and First Order banners being unfurled, while in the skies, New Republic vessels frantically turn on their hyperdrives and flee. After that, the film's original opening would proceed, albeit with a few new lines clarifying that the frequently-mentioned 'allies in the Outer Rim' are in fact these surviving New Republic vessels - which the tie-in material confirms is indeed the case - regrouping in a safer place, much like the Alliance fleet in the beginning of Mass Effect III.
*Add a short scene during the initial jump to safety where we see Leia using the Force to do something mundane, to hint that she's had some training over the years, and/or alter the way the so-called 'Mary Poppins' scene takes place. According to an article posted by Entertainment Weekly, the director said the idea behind this scene was that Leia wasn't actually someone who'd been trained in the Force, but that her powers manifested suddenly during this time of crisis, in the vein of "stories you hear about parents of toddlers who get caught under cars and they get Hulk strength and lift the car up." I don't find the explanation convincing, personally, and it's also another case where this is something in the film that would have benefited from a bit more information being given - for instance, at this point it can make a viewer wonder if Leia's had training beforehand in the timeskip between Return of the Jedi and The Force Awakens, when she hasn't. Plus, considering that such stories are the result of adrenaline rushes, it seems awkwardly reminiscent of connecting the Force to biology, and we all remember how well 'Midichlorians' went down with the fanbase...
As such, I'd add an extra scene beforehand just to show that Leia's got some idea of how to use the force to manipulate objects - and not just to sense 'disturbances in the Force', such as when Han died - or to have someone make reference to the fact that she's supposed to have some Force powers - for instance, perhaps Luke taught her something that she's using now to help them evade the First Order, like 'Battle Meditation'; introduced in the game "Knights of the Old Republic" and used by multiple Jedi characters - and then when the bridge attack scene takes place, instead of having her be blasted out into space with the rest of the crew - a scene that's unfortunately a bit hard to watch given Carrie Fisher's passing - have it instead that the blast badly damages the bridge; sending metal shrapnel everywhere and creating a huge crack in the window. Most of the crew would be killed by the shrapnel - including Admiral Ackbar - or be seriously injured, and then as they slowly get to their feet, we see that Leia is using the Force to hold the bridge together, and she's also bleeding heavily from a shrapnel injury. Everyone rushes out, carrying bodies with them, with Leia slowly walking backwards towards the door, the bridge starting to fall apart as her injury affects her concentration. She gets out and collapses as the bridge door seals, and through the window we see the room break apart and drift off into space. After that, Leia winds up incapacitated, and the film continues...
*Add more to Admiral Holdo's Plan to strengthen the payoff of her and Poe's storyline. In the film as it is now, even if Poe's actions hadn't derailed Holdo's plan, there are still many problems with the plan itself and the execution. If the film quickly identifies that the First Order is using tracking technology and not, say, a mole or anything like that, then why doesn't Holdo reveal her plan to the crew? If the tracking device can only track one ship at a time, and the ships are loaded up with escape pods that allow characters like Finn and Rose to easily reach Canto Bight without being tracked, why aren't they splitting the crew up and arranging to regroup later? If they flee to the surface of this planet with no guaranteed mode of escape, isn't that increasing the likelihood that the First Order ships will corner them? The list goes on.
In order to fix this, I'd make it that Holdo would actually explain her plan in the scene where she takes control...or rather, she'd explain A plan. Basically, she'd tell the crew that in order to shake the First Order off their trail, they'll be splitting them into groups and sending off certain members in space pods to nearby planet systems, and/or sending all of their larger ships in different directions with a skeleton crew aboard, and to do that, they need to continue ahead to a nearby hyperspace route, hence the need to keep pushing forwards. At the same time, she'd state that since there's a risk that there might be a mole on-board, exactly where they're heading will be kept a secret. In reality, her plan has another layer to it; as in the film, she's planning to get them to a nearby planet with an old Rebel base on it where they can hide. However, I'd add that instead of everybody being evacuated here, they're just shifting the heavy equipment, vehicles, important technology, etc, to that location temporarily. The real plan is for them to regroup at this planet once the First Order has taken the bait and gone after one of the larger ships, and then the others will turn back, pick up the group - and some fuel - and continue on to the Outer Rim...
The result? We still get Poe - and the audience, by extension - learning the important lesson that higher-ups aren't automatically clueless idiots just because they're opposing your actions, but we don't get viewers complaining about Holdo keeping secrets that didn't need to be secrets, or coming up with a plan that has more holes in it than Swiss Cheese.
*Keep Canto Bight, but change the circumstances of the visit. I imagine this is going to confuse a lot of people reading this. When I first started gathering ideas for this, I was originally planning to omit Canto Bight completely and instead relegate it to perhaps a cameo during the opening montage, but then something new occurred to me. The inhabitants of Canto Bight seem oddly relaxed and jovial considering that there's a war for control of the galaxy going on around them. If they're all fabulously rich, surely they'd be concerned about their assets on other planets, and whether they'd be seized or destroyed by this New Order? Homes, riches, businesses, etc? And then it hit me...wouldn't it be far more interesting if we have Finn and Rose on this planet and finding it odd just how peaceful things were here, then notice one or two weapons dealers who supplied the Resistance are here...and then realise that this whole planet is full of people who are backing the First Order as well and getting rich off the conquest, safe in the knowledge that their assets are secure? There could even be people watching news reports coming in of the war and making bets on whether the First Order will win a battle or whether a militia will last a few more hours, etc...we don't need a shot of a young child or an animal being hurt to let us know these people are only interested in riches.
So, that's one change, but as I said, I'd also alter the circumstances of the visit. At the moment, what could have been a suspenseful sequence about the Resistance fleet being isolated in space is weakened by the fact that Finn and Rose are able to leave and return without being spotted by the enemy at any point. As such, to fix this, I'd change the circumstances of how Finn and Rose met, and also how Poe comes up with his plan. Instead of waking from his coma partway through the First Order's attack, Finn would remain unconscious the whole way through, and would be on the medical vessel instead of the main ship. This ship would be severely damaged during the attack and they'd actually have to abandon it, so people would take Finn on the Star Wars equivalent of a stretcher and bundle him into one of the escape pods along with Rose, who'd have been a technician on that ship instead of the main one. As a result of the chaotic attack, it would launch early and send them rocketing off into space (har har) and they'd crash on Canto Bight, where Finn would awake in a fair bit of confusion - and perhaps even think for a moment that he's died, given that Canto Bight appears on the surface to be a quite nice place to visit.
After this, Finn would naturally be keen to find out where Rey's gone, and Rose would be insisting they need to get back to the Resistance group, and so since they're stranded together, they'd decide to make their way through Canto Bight to try and make contact with the Resistance and find a ship they can commandeer, and during this time they'd learn everything I mentioned above about the wealthy denizens of Canto Bight - which will in turn inspire Finn to aid the Resistance instead of going after Rey - and on top of that, see a group of First Order officers landing on the planet to make some deal with the locals...in a sense, they're doing Casablanca, and trying to get out of an occupied territory before the enemy tracks them down. Anyway, in time they'd make contact with Poe, who'd be sitting around on the main Resistance ship attempting to make contact with would-be allies, since he's got nothing else to do. The two groups would exchange information, and it would be from here that Poe comes up with his plan to get Finn and Rose to disable the tracker on the main First Order ship. Now, this bit could be done several ways depending on just how the earlier scenes went. For instance, if Finn and Rose have been away from the action this whole time, Holdo could be the one who knows about the tracking device and thus Poe could pass it on to them. Alternatively, if there are First Order officers on Canto Bight, perhaps Rose could overhear them talking about new tracking device technology, and thus mention that to Poe in order to give him the idea for his plan. In any case, their goal from here would be to incapacitate the First Order officers, steal their ship, and then fly back to disable the First Order's tracking device. DJ could still be included here in some form; since Finn and Rose potentially wouldn't end up imprisoned in this version, he could be a First Order prisoner who's already on the ship when they steal it, or they could run into him aboard the First Order ship instead, etc...in any case, the end result would be the same; the three of them en route to disable the tracker, just as in the film.
*Remove the scenes on Ahch-To where Rey follows Luke around. Not that there's anything wrong with these scenes, mind - aside from the fact that the scene with Luke taking the lightsabre at the start makes the timeline of events a bit confusing - it's just that the film is already very long, and with all the above changes already included, it'd run the risk of making the film a bit too long. Instead, I'd have Rey's first scene on Ahch-To be the one where she's practicing her lightsabre technique on the large boulder. At the end of this, the camera would shift to reveal Luke watching her, and he could make some comment along the lines of "Very impressive, but you're still wasting your time here." in order to set up his role in this film - although that being said, perhaps he could have taught her one or two things about lightsabre technique just to ensure she doesn't cut her arm off by mistake.
*Add more to Luke's philosophy, and justify his current state of inactivity. Much has been said already about whether Luke's behaviour in this film is a betrayal of his original character or not, but for me, the main issue with him in this film is that he never makes a compelling argument for why the Jedi should come to an end, or why there's no point in him returning. By his own admission, he 'created' Kylo Ren, and fled the galaxy afterwards as a result - which doesn't exactly explain why he left a map behind - but this begs the question of why he didn't - with the help of Leia and Han, and all the resources they had at their disposal at this point in time - pursue Kylo Ren to try and redeem him, as he did Darth Vader, or why he didn't try to kill him; instead he effectively left the problem for someone else to deal with. At the same time, Luke talks about the arrogance of the Jedi in assuming their philosophies alone are right about the Force, but he doesn't offer any suggestions about what should replace it, which effectively means that Luke is happy to let Snoke and Kylo Ren take over the galaxy and spread their own interpretation of how to use the Force just so that the Jedi can die off...because they were arrogant. To make matters worse, all it takes to change his mind at the end is for Yoda to manifest as a Force Ghost - something he and Obi-Wan didn't seem to have any trouble doing in Return of the Jedi, so it seems odd that he's only shown up now - and give him a short talk about how failure can be a great teacher.
Now, that being said, the Jedi certainly aren't perfect, and this has been explored over the years by many authors and in many formats - quite notably through the character Kreia in the game "Knights of the Old Republic II" - but the film doesn't attempt to explore these issues, and it feels like they missed a great opportunity here to give us reason to question whether they should indeed be allowed to die, and to be replaced by something new, as Kylo Ren is keen to do by the end of the film. As such, I'd have added a few more scenes where Luke raises legitimate issues with the Jedi lessons and philosophies, and brings this up as the reason why he's not wanting to teach her anything, rather than because he blames himself for creating Kylo Ren. I'd also have used this to explain just why he's on Ahch-To and why he left a map behind in the first place; after Kylo Ren fled, Luke decided to seek out Ahch-To in order to see if there was any ancient Jedi knowledge he'd previously been unaware of which could help him fix this mistake, and since he wasn't sure how long he'd have to train there, he left a fragmented map behind showing where he was going. Upon arrival, Luke read the ancient Jedi texts kept in the old temple, but found them to be so old-fashioned and full of all the problems that brought the Jedi down in the first place that he decided that they were a lost cause, and bitterly stayed in exile.
On top of that, giving Luke some stronger criticism of the Jedi would help explain why he doesn't think it's worth returning to fight against Snoke and Kylo Ren...would the Jedi be any better than the cause they preach, for instance? This would also work even better if Snoke's philosophy and methods were closer to the 'balanced' approach that The Force Awakens and the supplementary material promoted, but I'll discuss that more in one of the next sections.
*Expand the flashback scenes with Kylo Ren, and explain just how Snoke came into Kylo Ren's life. There's an important distinction to be made here. It's not necessarily crucial that we know just where Snoke came from or who he was - as many have noted, the Emperor's origins were shrouded in mystery for most of the series - but given that he is regularly mentioned by Luke, Leia and Han as being someone who corrupted Kylo Ren and set him on the path to the dark side, it's important for us to know just how he was able to do that, especially given that Return of the Jedi ended with the future looking hopeful, only for The Force Awakens to take things back to chaos without much explanation as to what was going on. On top of that, there's actually a lot we don't know about Kylo Ren himself; Luke says that he had the touch of the Dark Side within him, but that hasn't really been elaborated upon. What happened to him to make him susceptible to the Dark Side? Was it just teenage angst, or was there something bigger going on? I'd have added a slightly longer scene here with Luke telling us about Kylo Ren and whatever troubles he faced at the Temple, so that we can see just how he might have fallen under the sway of Snoke, who could have perhaps been something along the lines of a Force-sensitive user who survived Palpatine's purges and who developed his own philosophies, and who could have either corrupted Kylo Ren by creating a Force connection of sorts like the one he created between Kylo Ren and Rey in The Last Jedi and thus have spoken to him in this way - which could also be used to explain how he was able to create the connection with Rey despite never having met her - or who could have been a member of the New Republic Senate or even a member of Luke's Jedi Temple who quietly taught the impressionable young Ben Solo forbidden knowledge.
*Add some more scenes elaborating on Snoke's philosophies, and work the Knights of Ren into it. Did you know that Snoke's interest in Kylo Ren came mainly from the fact that he had a balance of the Light Side and the Dark Side of the Force inside him? Or that Kylo Ren is the leader of a group of like-minded Force-sensitives called the 'Knights of Ren'? If not, that's fair enough; both of these elements were hinted at briefly in The Force Awakens, and mentioned in far more detail in the supplementary materials, only to then not appear at all in The Last Jedi, which is a pity, because the idea of exploring a new philosophy that attempts to walk the line between Light and Dark is an interesting one...that's not to say that it would automatically be a better philosophy than that of the Jedi or the Sith follow, but it would be interesting to explore, nonetheless, especially if it's contrasted with Luke's own philosophy denouncing both the extremes that the Jedi and the Sith go to. A few extra scenes showing Snoke or Luke discussing these concepts would help both their storylines, and it'd also allow you to hint at what the Knights of Ren even are; for instance, perhaps Snoke is part of an ancient "Order of Ren" that stayed in the shadows and studied the balance of the Force while the Jedi and Sith fought each other? Were Kylo and the other Knights of Ren - implied to be other students from Luke's Jedi Temple - rebelling against Luke and his teachings for the same reason Luke now disavows the teachings of the Jedi?
*Either add more of a payoff to the Dark Side mirror vision sequence, or cut it entirely. At the moment, the sequence doesn't really add anything to the film - there's no real meaning imparted to the viewer, and despite Luke's claim that he can sense the Dark Side within Rey, nothing comes of it - so I'd either add something giving it a bit more meaning - exactly what I can't imagine at this stage - or I'd just omit it completely and use the time to let Luke discuss Jedi issues.
*Add a montage sequence during the final Force Connection sequences featuring random shots of both Kylo Ren and Rey. In the current film, Kylo Ren and Rey share an odd moment while en route to Snoke mentioning that they both saw each other's future, and Kylo Ren adds that he also saw that Rey's parents were nobody special in particular. I'd add a scene actually showing these visions of the future - perhaps in the same vein as the vision sequence in The Force Awakens, and containing similar clips - to give these statements of theirs more weight. On top of that, I'd also make sure that Kylo Ren says something about Rey's parents selling her to pay for transport, to explain why Rey's flashback had two supposedly poor junkers leaving on a fancy ship.
*Add some more scenes with Captain Phasma and BB-9E. The first one goes without saying, really; many viewers were disappointed with how easily Captain Phasma was defeated in The Force Awakens, and her battle with Finn was over just as quickly. I'd have made the fight a bit longer, for one, and I'd have also removed BB-8 commandeering the AT-ST; instead, I'd have had him attempting to access the hangar bay's controls in an attempt to help Finn and Rose, only for BB-9E to encounter him and engage him in battle! It seemed as though the film was setting this up to happen in the first place by presenting BB-9E as a foil to BB-8, so I found it odd that the character never reappeared after Finn, Rose and DJ were captured.
*Remove most of the battle on Crait, including Finn's near-sacrifice. Ultimately, coming so soon after several other battle scenes, this short battle doesn't accomplish anything - the ancient and decaying Resistance ships posed zero threat to the First Order and inflicted no damage - and ends up feeling like padding in order to give Luke time to arrive on Ahch-To, and indeed, Poe even notes they're basically just stalling for time. I'd thus change the scene around a bit; have the Resistance send their distress signal as the First Order prepares to attack, then get no response and prepare for a dramatic last stand, at which point Luke would show up to challenge Kylo Ren. This would also omit Finn's near-sacrifice; a scene which I have a number of issues with, but which would take too long to summarise here, so I'll leave it at that.
*Either have Luke be physically present on Crait, or have him survive the strain of his Force Projection. With the current structure, the film presents a somewhat strange order of events where we think a character has died, only for them to not have died, only for them to die afterwards anyway, which has the impact of making the audiences switch emotions so fast they don't have a chance to savour the moment. As such, if the film's goal is to kill Luke Skywalker by the end of the film, I'd have him be there on Crait for the fight, but if the goal is to keep him alive for part of the ninth film - potentially a smarter move given that Carrie Fisher's death has put Leia's appearance at risk - I'd keep him alive, but horrendously exhausted from the exertion of his power.
Oh, and I'd have made him use his green lightsabre rather than his blue one...the fact that he's using a lightsabre we saw being destroyed in an earlier scene means that either we'll realise sooner than expected that something's not right with Luke - thus weakening the surprise of Luke using his Force powers at the end - or we'll think it a film inconsistency - thus taking us out of the moment and weakening the impact of the battle itself.
*Either have the Jedi tomes being destroyed with the Temple, or omit the Temple's destruction completely. As a result of how things are presented to us, this minor plot sequence in the film inadvertently delivers a mixed message; first Yoda's use of the Force to destroy the Temple when Luke can't gives us the message that clinging to the past isn't the thing to do and that we should move on; the tomes aren't important...except later on the reveal that Rey has the tomes aboard the Millenium Falcon shows us that clearly they are important, otherwise they wouldn't have been worth saving. So the tomes aren't important except they are? I'd have the film make a choice and commit to it; either abandon the old Jedi teachings once and for all and forge something new inspired by what Luke taught Rey - thus making him the titular Last Jedi, and also the first of a new way - or have Rey take Luke's teachings and combine them with the old texts in order to find the right way to reform the Jedi Order.
*Remove the scene depicting the slave children re-enacting the battle between Luke and the First Order. Placed where it is, the last shot can't help but come off as somewhat confusing. The news of Luke Skywalker's Force ability, despite taking place on a planet in the middle of nowhere and only being witnessed by a handful of members of the largely defeated Resistance and several soldiers of the First Order who'd naturally want to keep this news from getting out, somehow is already news amongst slave children who'd have no access to communications systems? Instead of this, I'd go back to the opening montage I proposed first of all, and cut to various figures on the planets subjugated by the First Order who are all Force-sensitive - humans, aliens, children, adults, the elderly, etc - and who are already wanting to stand up to the First Order.
Oh, and it's beyond minor, but Keep C-3P0's arm red. Otherwise, you know, it's makes the inclusion in The Force Awakens completely pointless?
Who am I? I'm a random person who likes solving problems that pop up in various book/film/tv/game/etc series that I pay attention to. Hence, a lot of my work revolves around creating essays, maps, informative pictures, and the odd fan-fic to test out a scenario. I also like designing things, so there's the odd concept there too!
I'm only too happy to help out with things wherever I can...need a quick historical map drawn or want help coming up with a story concept? Send me a message and I'll see what I can do.