You know how Vader being Luke's father changed everything in the story of Star Wars? I feel like some gigantic revelation of that sort is required for any prequel rewrite or OT re-imagining to be interesting. Anyone can pick apart what shouldn't be in the movies, whether it be Ewoks or Jar Jar or even "But I was going into Toshe station to pick up some power converters!" But at the end of the day, changing these things doesn't change the heart of the story.
What I'm trying to get at here is that it looks like you're trying to go big with your changes. I think you're on the right track. My feeling is that you really need to go big with the heart of the story, make big changes that are risky, but have great potential payoff. I-am-your-father level changes to the heart of the plot, because the worst thing that this project can be is just the same story with some superficial changes and a new visual aesthetic.
What if Luke actually dies in his confrontation with Vader in Cloud City? Would Leia be forced to step into his shoes, and would she be up to it?
What if the rebellion contains the seeds of corruption that destroyed the Republic? For that matter, what is the rebellion even fighting for, precisely? What is its Declaration of Independence, its values and the type of government that it wishes to create or restore?
What if Luke learns that an intergalactic force is preparing to invade the galaxy? Would Luke risk destabilizing the current power system in the galaxy when it is about to be destroyed by an outside power?
Just some ideas about potential radical directions.