This isn’t really a fan-edit idea as it’s impossible (honestly I should post this in the rewrite thread, but figured it’d be interesting to the regular posters here).

I was thinking about TLJ recently and thought of a couple really simple changes that would’ve had a trickle down effect to improving the whole film.

Rose doesn’t exist. We just spent an entire film getting introduced to three really interesting main characters. Bette to build on that foundation than bog down this film trying to make us care about a brand new person that isn’t very interesting to begin with.
Poe goes with Finn to Canto Bight. These guys have a really fun dynamic that could’ve been interesting to see in action if they were on their little quest together. As it is it just reminds me of TPM when obi wan is on the ship the whole time, occasionally checking in with phone calls but otherwise doing nothing.
Poe and the codebreaker have a history. This could’ve eliminated that annoying video game style briefing Maz Kanata gives via space skype. All you need is Finn talking about how complex the first orders security is and that they’d need a code breaker and Poe says something like “I know a guy.” Then the next we see them they’d be on Canto Bight looking for the codebreaker.
DJ is the guy they’re looking for from the beginning. No need to make things overly convoluted. Just have them looking for DJ from the beginning, but maybe make him (her? i’ll get to that in a second) a bit reluctant to help due to some demons with Poe in the past.
Poe is the one who attempts the suicide run at the end. This moment made zero sense for Finn. However, since Poe’s character arc is pretty much all about him learning to not put others at risk for his own ambition of destroying the enemy (achem, the opening battle?), having him end the movie in a moment of self sacrifice only to be saved and told that it’s not about destroying what you hate, but saving what you love, actually feels like a natural place for his character to end up.
Phasma is tracking Poe and Finn. This is really simple. When Finn and Poe leave for Canto Bight, the first orders sensors see them and Phasma and a small legion of Stormtroopers follow them. This just adds a bit of tension to an otherwise bland b-story. Having the first order hot on their tail while they are already pressed for time presents a number of potentially interesting action set pieces, particularly on canto bight. It also gives Phasma something to actually do.
DJ is a female with a romantic history with Poe. If they really wanted a forced heterosexual romantic subplot like they attempted with Rose and Finn, might as well make it relevant and add some drama/tension to the bland story. If DJ is a female with a romantic history with Poe, that could’ve added an interesting Indiana Jones & Marion ROTLA dynamic. You could also sub her in for Rose in the rest of the movie. Having a natural rekindled romance throughout the movie gives the “That’s how we’re gonna win this; not by killing the things we hate, but by saving the things we love” line that was just awkward in the original some actual meaning and earned emotion.

Like I said, I know it’s not really appropriate for a fan-edit thread, since this is something that should’ve happened at the writing stage, but I just thought you guys might be interested in reading my thoughts and ideas.