From what I read on the devblog, the next update to Dwarf Fortress will make it the most realistic close-combat simulator in existence. Nerves being able to take damage, permanently impairing the motor coordination of one or more body parts? Hells yes.
Tabletop roleplaying systems generally make a point of not requiring you to track those sorts of things, because the number of dice you have to roll and stats you have to track (without messing up) get ludicrous quickly. But Dwarf Fortress, being a computer game, does not have this problem.
I think it would be nifty to use the Dwarf Fortress engine as a simulator "backend" for a tabletop roleplaying game. The players would roll up their characters in the game engine, and then the gamemaster would take over and put those characters in the appropriate situations as the adventure played out. When combat occurs, it uses the same system as in the game's current Adventure Mode, just with multiple characters under control. The gamemaster should be able to construct the world by hand if he wants, and then construct arbitrary situations for the player characters to fight and/or weasel their way through. But it would also be compelling to have your party wander around the same world as in Fortress and Adventure mode, going on whatever adventures the game master and/or NPCs set them up with.
(I am specifically not requesting network play. It would be very difficult to communicate about the game in progress without having all the players there. Perhaps not impossible, but crafting the appropriate interface for online multiplayer can wait until after version 1.0 comes out, I think.)
Besides, it would be neat to put a hydra and a horde of kittens in a pit and have them fight to the death.