My splatter at the wall wishlist:
In general, I'd like them to tie this movie into the whole trilogy, including direct references to prequel content. I want this thing to have its claws deeply sunk into all 8 previous mainline movies. Including references to Plagueis, and Anakin's conception. I want there to be a good long time jump between TLJ and this. I want the movie to get rolling relatively quickly, no need for a long establishing first act. We already know the score by now. And no time travel.
I want Sidious to have been behind it all the whole time. Somehow. Maybe he's been the one fanning the flames of the First Order spinoff, allowing the remnants of the original empire to die intentionally to give the galaxy a false sense of security (and to "cut the fat"). Make it so that when I go back and rewatch TFA and TLJ my perspective feels totally different. Reveal that the cloning technology for the Clone Wars wasn't exclusively for his political maneuvering, it was also part of his research into his own method of "eternal life." I want the final shot of his defeat to linger on his evaporating essence, like the T1000 in T2.
Snoke was somehow acting on his behalf, maybe unwittingly. His body could have even been just a malformed avatar/clone, being controlled/inhabited (which would make the Emperor's theme appearing in TLJ pretty damn sweet retroactively). I'll take a flashback involving this guy, sure.
The Knights of Ren, while serving Kylo at first, are later revealed to double as the Emperor's enforcers. Kylo thought he was in charge of them, but it turns out they were secretly his babysitters. They've been away tending to Sidious' schemes under the pretense of some other shit for Snoke. (And as soon as the babysitters left Kylo started fucking things up)
Kylo knows none of this. Emperor was operating in deep cover mode. Even his brain is full of fuck at these revelations. He's mad because he thought the sith were dead and that he was something new, but instead he was being used.
He shouldn't be traditionally redeemed. At most he should make an attempt to do the right thing, die trying, and then it's revealed that his actions played right into Palapatine's plan. Maybe he orders the Knights of Ren to fuck Palaptine up and the knights turn on him and kill him (as mentioned above), revealing he walked himself to his own execution when ol' Sheev was done with him.
Basically make him a casualty of Sheev's machinations with a sad end. A touch of redemption, but no happy ending for Kylo. It'll really fire Rey up.
Leia should die of a broken heart following Kylo's death. Just kidding. Whatever they can pull off with their existing footage is fine. It would be nice if she saw Luke's force ghost at some point I guess. Maybe in the finale.
I want Rey to get fucked up and lose part of a limb or something. It is tradition, but will still be relatively shocking to watch. She should not revive the Jedi directly. She should learn from Luke's lessons and found some sort of new order, focused on the balance/harmony Luke realized on his island. Playing up the idea that the tug of war between the Jedi and the Sith actually kept creating each other ("darkness rises and the light to meet it"), and that real balance is learning to accept and deal with personal "darkness" in healthy ways rather than trying to deny it entirely. Basically an order that wouldn't have pushed Anakin toward Sidious like the Jedi did. She survives the movie.
Give Finn more to do that actually has a tangible positive effect on the outcome of the movie. Make him more important than Poe to the plot. Give him a direct hand in the final victory. Maybe he actually sacrifices himself this time, but with a smile for his friends rather than angrily foaming at the mouth. It'll be sad and turn that weird scene in TLJ into foreshadowing. But I wouldn't be upset if he lives happily ever after, either.
Poe should just remain present as action support. I want him to stay close in a Rey/Finn/Poe trio this time around, but I don't feel like anything drastic plot-wise is necessary from him. Just keep the group together and let him be Action Pilot Man.
I want Phasma to come back one final time to cement the joke as the Kenny of the sequel trilogy. I'm only half joking. I would actually be down.
Lando should...be Lando. That's it. Lando's great. Besides however he is already involved in the plot, I hope he's present for the closing scenes of the movie.
It's probably a sure thing that Luke's force ghost will appear in the movie. It'd be nice if he appeared alongside Anakin together. Maybe they could use that sweet Disney/Marvel CGI to make him the same young age as Anakin. That'd be neat. It'd be nice if we saw his force ghost do something we didn't know was possible from one. (But that's not me requesting a force ghost lightsaber duel or anything)
I want Anakin's force ghost to appear in the movie in a way similar to it appeared in the Force Awakens art book, with the wild Vader visuals. (Which doesn't mean he's evil, we all know he was redeemed. But shades of Vader could appear in his visage were he to be recalling Vader in dialogue.)
Boba Fett shows up with Vulture-like jet wings and skeleton hands holding a large flaming sword and...okay no.
Has even one person so far mentioned Rose in seriousness? The shit circling her character/actress in TLJ on the internet was abominable, but that doesn't change that she was kind of a nothing character for me in that movie. So I'm not too surprised. But there's still a good way to utilize her here. Keep her around. Have her act as one of the trio's main contacts back at resistance HQ. "Guy in the Chair" status. That way she can still remain involved in an important position but more to the side.