Resource War TDM. Short and simple. The goal is to capture all the points around the map so you can spawn men there and take control of the vehicles, and each capture point is a resource hub like a gold mine, a farm, a quarry, a lumber mill. The gameplay consists of collecting as much resources as possible and killing/capturing flags and CPs for points, going back to base and dumping it off in your team stockpile. From then on, your team captain upgrades your base(s) and armory using the stockpile.
Upgrades would consist of making the walls higher, more defendable, buying vehicles, upgrading weaponry, unlocking spells 'n all that jazz. The only issue is that the enemy is free to waltz in and steal from your stockpile, meaning that needs to be defended, too. So you have the home team defending your stockpile and flag, and the offensive team capturing and collecting resources. Along with all this, you could set up a timer than slowly drains the stockpile as a "Maintenance fee". If you cannot afford the fee, things like holes in the wall or other obstacles will start appearing, making it so your home base needs constant upkeep or else you allow yourself to become vulnerable.
Both teams would be immediately locked in combat, and the only win condition is to control the whole map. This means that it would be quite literally a war, spanning several days, several players and taking and holding points would require some extreme coordination.
