Obviously, the negatives would be the best source. But given all the SE crap and the possibility that they may no longer conform to their original edits, and that the colour timing would have to be redone, it would also involve rather more work to put back together again, and every extra step is just one more potential place for LFL to screw things up. They don't exactly have a good track record, after all. So it may well be that a more 'secure' result would come from scanning interpositives or prints that already represent a complete depiction of the original films, even if the quality isn't as good.

Given Lucas' comments, I get the impression that if he ever did consent to restore them, it would be from separate sources than his SE's, which is good because then the two can remain quite separate, but also bad because they could half-ass it and claim it was the best they could do.

It seems to me that an ideal source would be whatever they used to transfer the first shot of the GOUT, with the pre-ANH crawl and the Star Destroyer flyby. Aside from being of non-anamorphic resolution, it looks quite good. Frankly, I'm amazed that they actually went to the trouble of scanning that shot and putting it in at all. I wonder what kind of source it came from . . .