I don't think it's by any stretch considered a classic, but the late 2E era trilogy of adventure modules in the Momstrous Arcannaseries that focused on Mind Flayers have a lot of potential for a reworking. The adventures were called A Darkness Gathering, Masters of Eternal Night, and Dawn of the Overmind. All were written by Bruce Cordell, and they were supported by The Illithiad Monsteous Arcana supplement.
The plot revolves around Mind Flayers trying to darken the sun, and it had a lot of cool elements. Definitely some weak spots and some flaws, but plenty of potential for a revision. If they did the adventure path approach, they could also include rules for psionics and possibly for space travel.
I think that would be a smart choice to go with...iconic villains, psionics mechanics, space travel rules, and it's not as well known so they wouldn't need to be slaves to the source material.