I've been working on a "Weird Horror" inspired megadungeon setting I'm calling The Black City; I drew a lot of the early inspiration from "At the Mountains of Madness".
Most elements in RoCC will be put right to use there; I can see using both Sea-Blooded and Sub-Humans as PC races. Some of the nasty custom monsters will be able to use the psionics rules. Artifacts and Grimoires are automatic.
I have a few entries on the Black City over at my place: The Black City