If confined without adjusting the previous movies (7 & 8) then I personally would not have a redeemed kylo and he is the main baddy due to the events mainly from Last Jedi.

He got rid of snoke, the one who manipulated him and was used (as Han said in 7) and when it was time to choose what to do … he wanted to stay as Space Nazi leader. Let alone wanted to “kill” Luke later … so pretty
Much without anyone manipulating him and being used by the dark side … he double downs on it.

(Of course just my opinion with the handling of Kylo)

So that is one, of the many many changes I would do if it’s strictly “rewriting” this movie. (Well honestly i would do a complete reboot of the whole trilogy, lol)