It wouldn't be so terrible to have turns processed serially to avoid the file collision problem. The PBW server for SEIV processes games like this, and a quick count shows 90+ games running currently. I'm not sure how DomII and DomIII multiplayer games would work, but as long as it isn't running as a pseudo-TCP/IP game (everyone online and playing at the same time, only sending turns via email instead of TCP/IP) all the time, serial processing shouldn't be a problem. Just set an upper limit on processing time, and require an admin to authorize over-runs for games where it takes longer than that.
If DomIII could be tweaked to prevent temp file collisions (directory for each savegame perhaps, store temp files there?), then you could have a very large number of games running on a modest box, the only thing to work out is the queuing to throttle simultaneous processing of turns, so each instance isn't starved out of processor and memory resources.
That's how I see it anyway. I could be missing something obvious about Dominions multiplayer, having only played the demo for Dom2. I soon plan to be educated with a full copy of Dom3 though
