Haven’t read all the other good ideas yet but here’s what I’d do if I had some mad motivation to turn this into a watchable movie:

Let the attack on the dreadnought (correct spelling?) be a success and not require the sacrifice of Asian girl #1.
Let Lea die. Let Kylo kill her.
Let her successor be a traitor. (and maybe instead let that young pilot do the kamikaze?)
Let Luke die in the first laser blasts. No fancy speeches.
Do something about Snoke’s death because it is preposterous and illogical.
Remove Rey beating Luke.
Let Chewie eat that thing.
Reduce Luke’s whining
Get rid of force ghosts blowing up stuff. (Yoda says “Those we teach shall surpass us” but he far surpasses Luke even in his death, so what’s the point? Besides, it’s pointless anyway.)
Stop Asian girl #2 from bullying Finn.
Let the resistance be rotted out almost completely.
Overall reduce grrrrl pwr.
Let Kylo defeat his enemies on his own in the throne room.
Do something about the end of Kylo’s and Rey’s confrontation. Maybe let him let her get away, in an act of mercy or something?
Remove Kylo being bossed around by that Imperial dude (what does he possibly have on him anyway?)

Of course this would completely break continuity with IX. But oh well.