I'd be inclined to have the game run in a pseudo-turn-based format. Let each player's fort run through an entire season over the course of a real week, being paused and restarted as they play. Any interaction between forts would take place with a substantial delay, so at the end of a "turn" you'd have war parties departing, trade caravans embarking, migrants or hired help headed for other forts, etc. Over the course of the next season, these groups would reach their desitnation.
So I get fifteen soldiers and send them out against the local kobold camp the slaughter the populace and claim their...novelty...crafts... and I also send a twelve-dwarf trade caravan, with four wagons, to a buddy's fort, loaded with the bauxite and wood he needs, with instruction to buy only flux stone, sand and glass from him, no more gypsum mugs and narrow socks.
They head out toward the end of the season, and some time in the next season or two (depending on distance) they arrive at their destination, and the target player deal with them. A season or two later, they get back home, with spoils, slaves, casualties, treaties, news of map features and an update on the place they visited.