Unless I’m remembering wrong, they said Leia was sending one final message to Ben before she laid down to die. I took that moment as Leia’s spirit literally going to Ben to save his soul (and that’s why he sees Han after her death, because she’s the one showing him), so when Ben died at the end it made both bodies vanish because he took her with him. I’m sure I’m dead wrong but that’s my thought process.

My only ideas for edits would be

inserting prequel planets in that montage they had with ONLY original trilogy locations.
inserting at the very least Ben Solo with Luke and Leia on Tattooine somehow
Carrie Fisher often said her lightsaber color would be purple, so maybe simply change the color of her saber to add a little bit of her flavor to it so it’s not only blue and red
maybe cut Finn’s “I never told you” stuff altogether since they never conclude that, but I’m pretty sure what we’re supposed to get is him having the force cause how else could he have felt Rey’s death like that
go to ImmersionVFX to give lightsabers to the Knights of Ren like with the Praetorian Guards since they’re heavily implied to be previous students of Luke’s
and yeah cut the kiss