Different, more uneasy relations between Lando/Han/Leia. This would be exacerbated by Han's being frozen for so long. It would add some more conflict to what are some pretty peachy relations. More discussions between characters.
Luke is more of an outcast in the group, until the very end. He has spent the time between movies (mere weeks in this version) at Dagobah, he's the last one to arrive at Tatooine, and he's (of course) absent for most of the battle. Make it understandable too. Vader TORTURES him mentally, constantly trying to get inside his head, throughout the whole film until he surrenders on Endor. Also, give him some scars from his brawl with Vader in the last film.
No Ewoks. Not even replacements. There are more troops for both sides deployed on Endor, and we get some interesting combat,. Mainly, AT-AT's and snow speeders fighting on the ground. Lando and CHEWBACCA are up in the air, so one new character and one character we care about up there, to increase tension. Han gets shot early on in the battle, and Leia continues the ground strike on her own. R2 is shot, possibly even in worse shape than in the final film. Leia destroys the generator on her own.
No change to the Vader/Emperor/Luke stuff. It's perfect as is. Just change the final outburst a bit, to accommodate my next change...
Luke and Leia? Not related. Yoda's promised "other" from ESB is kept ambiguous, a mysterious promise for another tale.
Luke claims power for the rebellion via a mass announcement, before Death Star II can explode. The big destruction for the movie is the Executor, which goes out in far more of a bang. Namely, Chewie and Lando cause it.
The film ends with Luke having a final convo with Ben on Courescant, where Ben discusses his pride in Luke for finally redeeming his father. And right before Ben fades out, he catches a glimpse of a man in robes, clearly his father. They both fade out, and Leia and Han come out, Han's arm in a sling. We hear that Leia's in power now, queen of the galaxy. The three share a conversation about their adventures, and the films end with the three of them staring off into the distance, together, once again.
What do you think?