It'd be a perfect tie in to where the Return of the Jedi leaves off.
Definitely the Thrawn trilogy, OMFG would that be amazing.
That would be the best thing to happen to Star Wars in forever.
Except the Thrawn Trilogy used Luke, Leia, and Solo extensively. I can’t imagine any of those actors coming back to reprise their roles.
However, they do have to use Thrawn in whatever series they do. He’s just too awesome a villain not to use him.
There’s also the Knights of the Old Republic series (video games and comic books). Excellent stories.
Plus with no union issues to worry about, some real established talent could be brought in to make these movies.
I loved the Zahn books. Most other Star Wars novels seem like crap.
Obviously any post ROTJ movies will find it difficult not to trash the continuity formed by all the novels, not that that would be a bad thing.