How about a minigame that can only be accessed every 6 hours, reduces the expedition timer by 6 hours if it's won, and also has a difficulty increase for however closer the timer gets to being done. it'd take a full platoon to win a > 6 hour timer, 3 and a half squads for > 12, 3 squads for > 18 hours, 2 and a half for > 24 hours, 2 squads for > 30 hours, 1 squad for > 36 horde/defense would be pretty easy, defend the payload or miner, takes something like 30 mins to an hour to complete. Maybe a "clear the obstacles" game mode, where you're pulling objects off a road, while also fighting NPCs that set a trap, using ANTs to clear debris. Even if it wasn't NPCs, you could have expedition raids among outfits, and the winning team can have their timer shortened.