I would not support replacing any actor in the OT with an actor from the PT or anyone else. Such an act would be sacrilegious. But after seeing ROTS, I would definitely support lots of other changes in the OT, mostly in ANH. Yes, that would mean modifying the OT more still, but that doesn't matter to me anymore. I want the Classic Trilogy on DVD, sure, but it doesn't seem we're ever going to get it. So be it. That being the case, we might as well have all six films as closely matched as they can be.
I put in ANH after coming back from ROTS--just to see the episode immediately following--and to be honest, I couldn't help but be rather bored by it. Those dazzling visuals Lucas has used for the prequels have spoiled me. The storytelling, performances, and chemistry may be superior in the OT, but even with the changes Lucas made for the SE's, the look and feel is still very dated. Still very late '70s/early '80s. Even some of the music could use a little reworking. When you watch the episodes in chronological order, and you go from ROTS to ANH, there are big changes that actually don't sit well with me.
There are a few things that I think would go a long way. Replacing all models--Rebel fighters, Imperial fighters and ground walkers, Star Destroyers, the Millennium Falcon, etc--with CGI. Reshooting the Battle of Yavin. (When fighters crash into the Death Star, show the fighter itself impacting on the surface rather than just the explosion.) Reshooting the AT-AT assault on Hoth. You get the idea.
One addition I would love to see is a more dramatic introduction to the Death Star. In the final scenes of ROTS Darth Vader and Emperor Palpatine stand together and look on as construction of the Death Star begins. The next time we see it is in ANH. The scene shifts to an approaching Star Destroyer, then cuts to a two-shot of the Star Destroyer moving in on the Death Star. I feel like something of the Death Star's importance should be unveiled, not simply shown. There's no shot in ANH that does that. First time we see it is for a couple seconds in a static image.
Those are the kinds of things I would change. Just make the OT more visually stunning, as close to the level of the PT as possible. Now as for Obi-Wan's comment that Luke's father wanted him to have his lightsaber when Luke was old enough, and other such obvious inconsistencies with the PT, I have no idea. There are probably many of those present in the OT now.
And yes, I'm sure I'm in the minority with these ideas.
Changes keep coming, and these are the changes that I would love to see. Leave the original actors and their performances intact, but spruce up everything else. The human spirit of the OT is kept alive, while the look of the PT continues, and you don't feel like you've gone backward in time as opposed to 20 years beyond the last prequel. Just my thoughts.--THX