I might also consider a few cut scenes (Biggs/Luke on Yavin) but nothing dramatic.
I can only think of one instance off the top that I would create and insert, a new Palp holo in ESB...but it would have to be much better then the one currently in the DVD's.
It's a shame he didn't think as much of his OT as most did, I would have bent over backwords to try and make the prequels as faithful as possible to the OT, and never would have had to go back and alter anything.