Bob Garcia has been working on that, based on a suggestion of Angel, who realized that the weird look of the emperor in ROTS can be corrected (in part) by altering the proportions of his face. Another thing to do is to make the glow of his eyes a lot softer.

Doing this you won't be getting an exact replica of the ROTJ emperor but he'd be far more similar to it, and you could always blame the 25 years of aging between the events in ROTS and ROTJ for the differences between the "young" emperor of the PT and the OT one.

Check the video. http://www.youtube.com/watch?v=eUBodCHtMBU