Between the AFI, BFI, and the Library of Congress, there are several archival quality prints out there. (That Lucas won't allow to be screened.) If the negatives really were dismantled in the process of making the SE's, it's not impossible to do something with the prints.
It would not cost millions to scan the best available prints and clean them up. If Lucas would let Criterion do the OT and THX-1138, I'd be a happy camper.