Aside from the obvious things like removal of the emperor's "slugs" (how many years have we been asking for this one? lol) it might be cool to touch up the emperor's eyes.

Perhaps make them glow as they do in RoTS. Especially when he is shocking Luke.

"m really intrigged by the idea of changeing Vader's line from "Obi-Wan once thought..." To "Your Mother once thought as you do". I really like this idea"

^^ I've always liked this idea. It is a great PT tie-in. If it can be edited properly to sound natural I'd say go for it.