You can go into the same themes and ideas:(natural world is better, industrialised is bad) without getting too close to those Shinto-like ideas Miyazaki explored in Mononoke.
Isn't it funny though how closely related all the talk from Yoda about the Force being tied to all living things can cover much the same ground?
Originally Lucas had the idea of Had Abbadon, home of the Empire, being overpopulated. It was a city-planet. Endor was nearby and was being cleared for resettlement of people from Had Abbadon.
So my suggestion is to try and keep the spirit of Lucas' original idea there with some sort of action by the Empire that causes a timely dilemma for the Ewoks.
I like the idea of the Empire plundering it for resources for the DS2 because it would be easier to accomplish and would be less clunky than force migration of Imperial citizens to a forest moon.
It would also give us an opportunity to show a scene or two of the damage wrought by the Empire.
Maybe the rebels go through a section of forest that has been clear cut? Maybe the speeder bike pilots the heroes confront early on are parked in a clear cut area or something?
Then you could have a scene showing the heroes a rusted out AT AT or something.
So first establish: Empire ruining the planet.
Then establish: something here is fighting back. But what?
Then Leia meets Wicket. What? These guys? Come on.
Then when we see them in battle we're like: S***! These Teddy bears are little versions of Wookies.
I also like the idea of the Ewoks facing a threat. A perilous threat to their way of life and very existence(like losing their forest, their home).
ROTJ should up the ante waaay up. It is the climax and should show how dastardly the Empire can clearly be.
I dislike how ROTJ just bums along. And the Empire doesn't really do anything particularly offensive.