tl;dr: Pitching a communal fortress mode playthrough. Different folks assume different roles, one person processes the turns (by month or by season) based on instructions from each player.
First a quick disclaimer; although I'm not a fan of folks posting grand ideas, but whom don't have the capacity to champion and lead themselves. But I'm going to do it anyway. I'm hoping someone else will like this idea and take up leadership of it, and I can be a participant.
So my idea is this, based on a successful multi-year phenomenon that we ran about 10 years ago with Space Empires IV: We play a multiplayer Fortress game. We all play the same fortress. Instead of taking turns as with a succession game, we all play at the same time.
One person would be the leader, or Overseer if you will. This person will do the work of issuing orders to the dwarfs, and merging instructions from all the other participants. The Overseer would upload the save game each month, or each season, and then wait to get instructions back from each player.
The players would take on different areas of responsibility. This could be something like "architecture, z-10 to z-12". Or it could be something like "Military squad: The Tombs of Loving". Or it could be all Masons. Or whatever.
I am imagining that players in charge of architecture would compose layouts in QuickFort, so that they could easily be applied to the game. A coordinate system would have to be devised so that peoples' layouts would match up, and maybe one person would be in charge of common connecting shafts and access ways.
Maybe one person would be in charge of traffic management systems, another could define boroughs, another zones.
If there a small number of participants, then each one would have broader responsibilities. More participants would make each person's job more nuanced.
There is the opportunity for "abuse" as there is no real way of stopping people from "playing ahead" before issuing their orders, but it is mitigated by the fact that they cant predict other peoples orders or how the Overseer will implement their instructions.
Backroom deals and politicking can occur on a forum thread for the game, where players would barter favors and try to build support for their plans, or vie for territory (who will have control of the newly discovered caverns? what happens when the military leader tries to draft your weaver?)
So... Any takers? Anyone want to step up as the coordinator?