Octorox said:

You can't really kill of any of the major characters because the new emotional arcs and endings required for the other characters aren't there. You'd need to shoot a whole new movie. The again, I'm surprised Leia wasn't an emotional wreck for all of ANH after her entire family and planet was wiped away....seriously one minute her life is turned upside down, the next she's making witty banter...

I think you've hit the nail on the head as to why a lot of the more radical ideas just plain don't work. Yeah, there's no harm in it as a "what if" concept, but if you were to actually try to make some of these changes, like killing off a main character or moving the final battle to Couriscant, you would have practically film a new movie just to make it work, and the logistics of that are not very good if the goal is seamless integration. At best I could see such changes being jarring, and ultimately it's the exact kind of thing that we complain about Lucas doing too much.

My general ethos around fan editing is to accept the stories for what they are, and see fan editing as a tool that allows the story to be better told. Outlandish changes can be great if you're willing to accept that they won't be perfect, which is why TMBTM's grindhouse cuts work so well, even though they're drastically different from the original versions. If you're going to try and drastically alter the mythos of the original though, for me that's sort of walking on thin ice. If there's a change that is really necessary and it's possible to do it without breaking the illusion, then I say go for it. If it's a change that does not benefit the story significantly though, and it requires a lot of suspension of disbelief on the audience's part, then I feel like it's probably something better left unchanged.