I think the extras disc for each movie should contain its original making of (The Making Of Star Wars, SP FX: The Empire Strikes Back and Classic Creatures From Return Of The Jedi). I would also include the trailers and the deleted scenes from each film. Also the laserdisc extras for each film. Some picture galleries would be nice, too.
It would be necessary a 4th disc for "general" extras. It would include "From Star Wars To Jedi", some auditions, Return Of The Ewok, Star Tours (yeah, I think it's time to release this on DVD) and some other small stuff.