The word came yesterday that the Star Wars spin-off movies will be origin stories. I don’t know that will be the case for all of them. Boba Fett’s origin is already laid out in the prequels and he’s one of the first names that comes up for a spin-off. Some characters I don’t really want to know their origin. I don’t want Baby Yoda. But some would be great and for the first, you’d just have to adapt James Lucerno’s Darth Plagueis novel (it’d fill in a lot of prequel holes as well).
3. Han Solo (you could roll a lot of Lando and Chewie’s in here as well)