It wouldn't be a big deal, Lucasfilm just uses that as an excuse. There would probably need to be some significant color correction done since it is probably faded quite a bit by now, but yeah, the 1985 IP is just one of many sources that are viable for a new, high-def release.

As for the original question, the 1995 THX release is the same print used for most other home video releases (all of them?), the reason it looks better was because the telecine was optimized by THX standards and it was the first time the films had been mastered digitally. As a result the films are crisper and cleaner and have better color and sound quality than the previous releases.

Does anyone know if it was the same master from the 1993 DE just re-mastered and re-transfered, or was it a whole new telecine from scratch? The DE had the ghosting issues from the dirt concealment, but is this on the THX sets as well? If not, my question is why LFL used the 1993 version for the GOUT, since there was a HQ master made for Laserdisk for the 1995 set as well.