I like the twist... LOL at night, now that would be funny people cracking limbs and tripping over branches rushing toward the fort. Think Brave Heart with people tripping.
What I would do is this... My crew has this funny prop (A Big Blue 1000lbs Bomb) you could plant that anywhere in the field and not tell anyone where it is. Both teams start at each end of the field and go looking for it. HEHE, now you can see teams use scouts and force recon. When that team finds the bomb they broadcast up the chain of command and General announces it to judge and over channel.
At that point each team regroups and the team with the bomb now has to setup a FOB (Forward Operating Base) and defend the bomb. They are given 1 hour to prep (assault lines, booby traps! lol (From Goonies))
The key is the other team is not told where it is; they have to go find it. This could take hours depending on the field size. Once found, battle royala!
The defending team can resupply as much as they want, they just need to get the supplies in and out without being killed. Any supplies capture can be used for the assaulting team. Also the defending team can have no more than 3 lives and a medic must heal also if medic goes down the can touch to bomb to get a life.
Hell, this sounds fun already! This is perfect for snipers and assaulting/defending.