Well, for me the ultimate set would include the original theatrical versions along with the final Lucas versions for each film. A commentary track for all three films that included Lucas and other key production folks as well as an actor commentary with Hamil, Ford and Fisher.

Each film would have it's own special features disc that would include deleted scenes, all trailers, TV spots, galleries, and the making of specials that aired on TV. The Empire of Dreams documentary would be split into three different documentaries and each would be 2hrs long and focus specifically on each film.

Other than that, I can't think of anything else that the set would need to have. At least in my eyes. A John Williams commentary would be nice but not necessary.

Perhaps as a mail in bonus you could send away for the Holiday Special. That way, only the real die hards would send away for it.