Frankly, I can’t imagine how a Cthulhu MMO could be done “right”, at least based entirely on the original Lovecraft stories. Cthulhu Mythos stories are largely about being slowly stripped of support (and “innocence”) and facing the powers of the eternal night utterly alone. The protagonists in most Mythos stories are lucky to end up stripped only of their sanity… most of their colleagues lose their lives, and most encounters end up being characterized by “I ran away fastest, so I survived.”
An MMO that tried to accomplish the same “ambience” would almost perforce need to be about exploration, as opposed to conflict. Perma-death would be a given to be true to the Mythos. And the idea of having to generate enough content to accommodate even a few thousand people in such a system is a thought that has me making real-life Sanity checks…
Now, one potentially interesting concept could be a game with a slightly different tack, moving to the sometimes hinted at larger conflict behind the scenes, similar to the Call of Cthulhu RPG. Players are working to either prevent the Old Ones from awakening, or are working to release them. Guilds are either cults or cult-hunters. Conflict generally occurs between humans and humans or humans and lesser Mythos beings. If an Old One is successfully awakened, the “world” ends, all characters die, and a new instance is formed.
It’s a depressing game, true to the Mythos. There can be many small victories, but no way to ultimately “win”… and one significant failure means an utter defeat and loss of nearly everything. That could be mitigated with reward systems on the account level instead of the character level, with carry-over to the next instance when a world was consumed.
It would be an interesting undertaking, definitely. The type of boutique MMO that could be fun if done right, but would probably never generate the cash to make a big production house consider it. Not to mention potential licensing costs: but maybe Chaosium holds those rights too, and a deal could be worked?