For starters, the sequel trilogy needs to be made to be more cohesive on its own.

The Last Jedi is the only one of the three that actually tied back to the original saga (apart from resurrecting the villain in 9), and 7 and 9 should be bent to be more in line with it.

Palpatine should be built up over the entire trilogy. I know that the OT doesn’t have the Emperor until 5, but TFA is too weak to stand on its own without it. If this were done, he would be in every Star Wars except for the original.

Hopefully we get the extended cut of 9, so we have more to cut down from. Really, if we can make 9 into a better sequel to 8, our only problem would be 7.

As for the prequels, they just need to be edited better, cut down to about 2 hours each before credits.

Editing the OT to be more consistent is a good idea as well. Cutting scenes from Jedi where Han is out of character would improve it a lot, and cutting the terrible scene where Leia kisses Luke (which was bad even before Jedi came out) would tie it together well. Some of the SE changes that aren’t terrible would do well being kept, such as Victory Celebration and extended flying bits, though I am not sure about Hayden at the end of Jedi.