I like the partially destroyed Death Star idea. It could even be established in ANH that Yavin is actually Endor (just change the one line in the film establishing this), and it makes sense that the damaged Death Star would remain in orbit around the moon.

There is the issue of Yavin 4 being more tropical than the Sanctuary Moon, but you could even fix this by making the matte paintings more deciduous. Being incredibly bold, you could film one or two people in Ewok costumes and have their shadowy forms peeking out of the woods at this point:

So now there’s a reason for the Rebels to protect the planet rather than immediately evacuate, as there’s a native sentient species, and there’s a reason for the Ewoks to treat Leia as royalty, since she may have been known to the Ewoks as a leader of the Rebellion.