Regarding Ewoks in ROTJ, I remember seeing something years ago, that Lucas originally wanted to make a planet of Wookies.
It could’ve been on a Discovery Channel program. However, since the Chewbacca costume was made of horse hair, and was extremely expensive, they had to change it completely. Make a planet of small creatures, using less expensive material. The name Ewok came from Economical Wookie = EWOK.
Having Wookies would have made the Battle of Endor more enjoyable to watch and more believable but I still feel as though the time that was spent on the Ewoks should have been allocated to the trio.