I think this is already being done...you might wish to check with the Citadel project (assuming they have not shut their doors).
I personally would suggest a Pathfinder CRPG, as the true successor to NWN. To boldly go, where no CRPG has gone before!
Word.
Give us what we want - a simple to use toolset, a complete DM Client, a Server-side Client, an open source framework, coupled with Pathfinder ruleset and IP (models, etc). And, of course, an explosive, complete OC! Yeah!
GIVE IT TO ME, BABY!