Unlike ANH, I don't think these movies require as much work. Aside from fixing the most jarring fx shots and the lightsabers, as well as to remove the worst Special Edition aditions, there really isn't much that needs to be done.

Personally, I would darken the Emperor's hologram A LOT in ESB. The Emperor's face is gradually revealed in ROTJ; it starts out entirely in shadow when he first arrives and we don't get a close-up until Luke arrives. In a way, we se Palpatine at the same time as Luke does.

This gradual reveal is IMO ruined by clearly showing his face fully in ESB. In light of the PT, it could be called a gradual re-introduction. Either way, the Emperor hologram should be changed to be more mysterious.