Why not just completely redo all the special effects of the entire OT? Go back to the original principal photography footage, digitize it and then set the ILM folks on it and literally create brand new effects, etc. Essentially, all the stuff involving actors would be the same (just enhanced a bit) and all the SFX would be brand new. Also, bring John Williams back in to re-record the soundtracks to better fit whatever changes occur.
Basically, Lucas would be making brand new movies.
Oh!!! And include the original theatrical versions with them when they come out on DVD.....that is a requirement in any case.
For some reason, this seems like a no brainer when you think about it. I would love to see newer effect set to the old movies. It may or may not make the movies better, but I would be curious as all hell.