Actually, what'd be nice if it were a Wurm-esque way.
Each person controls their own seperate dwarf. There is no one player that rules as "supreme entity", rather, they all collaborate to build the fortress together. It could be from a sort of adventure mode perspective, only continually updating. Probably at a slower timescale than dwarf mode, but faster than adventure mode.
I think it'd bring DF to a whole new level... plus it'd set the grounds for a full fledged Multiplayer mode based off of this. You can adventure alone, or gather a bunch of friends, obtain some items, and set off to make your own fortress. Or, you can adventure with friends too. All in a massive persistent world. But obviously many, many changes would need to be realized before such a thing were possible.
Plus as a side effect, you could build a fortress solo, if you really wanted. It'd just take a while!
It'd be interesting to figure out how a mood would work. I suppose the best way is that you lose control of your character until the artifact is created... because, if you were shown a list of items you must obtain, you could just tell your friends specifically what you need. Impossible to lock down any means of communication. Players would find a way of circumventing it, like IRC or something.
It could take a new concept, maybe a puzzle-ish way or something.
[ October 08, 2007: Message edited by: Lightning4 ]