Honestly, that would be fun in a weird way... have each "day" be about 1-2 hours of a standoff and the attackers basically have to keep the defenders in until their food supplies (which would be kept track of by an admin) run out or they decide to surrender. Each attacker gets 3 lives, each defender gets 1 or 2. To win the attackers obviously have to capture the fort/town or force the defenders to surrender (either by keeping them trapped until their food supplies run out or by simply battering them into submission). The defenders would win by either killing off the attackers or getting them to give up and retreat. Defenders don't have to stay in the fort/town but it's probably the better idea. Also, members who quit in the middle of the game are considered deserters (crashes don't count) this can be another factor of the long, drawn out siege warfare.