1) Ewoks switched to Wookies
2) Endor moon is far more protected with the brush cleared away from the 'back door' as most military people would do. To dangerous having all that cover around.
3)Sandstorm subplot would be reinserted. During that time, Luke discusses how he continued training after he left Yoda, refining his skills as they hunted for Han Solo across the galaxy.
4)Subplot of the Alliance seeing Solo, Skywalker, Leia and Lando as insubordnate outsiders. They left the fight against the Empire to go looking for Han Solo. I would not welcome them back to the cause without reserve. Make the plot point that they agree to go on the Endor mission to re-establish good faith between them and the Alliance.
5)Boba Fett jets off of the barge once the s**t hits the fan. We have a shot of him falling back to Jabba's side. When it all starts to fall to pieces, Leia still strangles Boba Fett. Jabba looks at Boba and insults him while asking him why he does nothing. Boba Fett shrugs and walks away. Last we see of Boba Fett. Make it less personal, more business. As the story flows now, he's dealt with Jedi and wishes not to do so again.
6)The finale on the Endor moon should not exist. The scenes of the people rejoicing throughout the galaxy should stay in. However, have the principles talk from various ships (ala ESB) and go their seperate ways. The Tatooine scenes feature Luke returning home as the people rejoice, Leia and Han returning to Corscant, Lando to Bespin...you get the idea. Have this grand story end with it truly being a tale of misfits who came together at the right moment and saved the galaxy. From there, like all great warriors, they must return back to the world the left. They are different, but the place they left is not.
7)Luke burries Vader at the Homestead. The circle would then indeed be complete. Final shot of Luke looking out at the twin suns of Tatooine. Wipe, Credits.
That's just some of the stuff I would do. Lucas really skimped out on some of his mythology character traits in the final film. Not sure why.