Not that it has anything to do with Solo, but as far as real-world stuff for Ewoks and such...? Best I've been able to piece together from everywhere over the years is: George had hand-scribbled notes in notebooks, much crossed-out and revised from high school on. When he wrote the script for Star Wars, there wasn't anything like a fully-fleshed-out story. He took the elements of "Death Star" and "Wookiees" from the end of the story to use in this one film, because (he figured) it didn't matter. He was only going to be able to do this one, so there was no reason not to plunder.
So. Once he'd had to follow-through and do more Star Wars, once he'd gotten tired enough of it to cram the last four episodes into one (and forget about ever doing the Obi-Wan episodes), it seems to have been a perfect storm of creative and practical concerns. On the one hand, the question of finding enough tall people was brought up (but never explored, or they would have found, then as now, that there are plenty). On the other, George's ongoing fondness for making use of Little People is well known, and that factored in. On the third hand, the bit about Chewbacca having been developed far afield of the original thumbnail of his people factored...
So George decided to invert the Wookiees (literally -- "Ewok" pretty much just swaps the syllables) and make them very, very small instead of very, very tall. He further gravitated to the more teddy-bear-like designs for the visual disparity of these cute little things being what overwhelms the mighty Empire (a very brief skim of George's filmography instantly let's one know he's a fan of underdog stories).
I have many depressive 'what-ifs'. Expanding ROTJ back out into four episodes would have allowed so much more breathing room for the narrative. Keeping the Wookiees, as intended, as slave labor works. They can be technological beings, just denied access to technology by the Empire. Especially if they were transplanted to this world for the construction project. I, personally, like the idea of Our Heroes stumbling into where the Wookiees' children are being held hostage, to keep the adults in line. Left to themselves, they've gone all Lord of the Flies and capture Our Heroes. Could even still have Ewoks played by Little People as natives to this world, if you really wanted to keep them in the lore...
Anyhoo.
--Jonah