For ROTJ,

Maybe Leia could be found by seven Ewoks;) Very much has already been said about the difference between cute and cutesy. Wookies are cute. When I think of the Ewoks, I think of Bobcats. Tree dwelling predators that are very cute.

The shield around the core has been mentioned here. It's the only way I know to get all the story lines to climax together. It creates possibilities for a really neat "Shoot-out at the OK corale" sort of thing with the ships hovering and firing at each other when popping up from behind conduits and so forth.

The shield falls when the Emperor strikes it? That might have to be set up back in ESB with Yoda exposition about the Sith master able to focus all the darkside power of the galaxy within his person. Vader might have to repeat the same idea to Luke. It would help explain why Vader doesn't dare defy the Emp alone. Vader might make another attempt to recruit Luke to overthrow the Emp while on Endor.

In the project conception, Endor was a world with gravity about 1/2 or 1/3 that of Earth. That impression might be easier to create with mod FX. It might explain why the trees are so fantastically tall. The trees were a bit alien looking with great diameter trunks. A very alien forest primeval feel.

Endor located high above the center of the spiral galaxy? That could create a really neat spider behind the Emp in the Throne Room.