Peter Serafinowicz as Thrawn. And not just his voice, either.
Too young IMO, but perhaps in 10 years....
Viggo Mortensen as Talon Kaarde. Good and evil in one neat package. I really miss this guy as a non-hero!
Barring him, I'd love to see Treat Williams do another antihero role, this is close!
Ahh! This I like!
Sean Bean as Pellaeon--with or without beard?
Had Bean been less well-known, perhaps, but I feel like he's too famous for this role... needs to be someone less recognizable IMO. Also, Pellaeon doesn't die, so no.
Nathan Fillion as Han Solo? Anyone?
Depends on the tone of the movie. If the director wants to combine the comedic relief of Binks/Threepio with the roughness of Han Solo, then perhaps the Firefly-esque Fillion could pull it off. Definitely not the Castle Fillion though - too immature.
Clancy Brown as Jorus C'Baoth.
Possibly, but he might potentially be too typecast for the role - C'baoth isn't supposed to be a rankled and rogue US military general, and that's all I personally see when I see Brown's face...