Why not just an elephant as it is? Obviously health packs and ammo would spawn on the elephant after each round, just like on other maps, maybe stick some more cover on it and some more ways onto it for the covenant, (the AI probably can't manage to climb up the sides as it is at the moment).
Add this to a map with structures that can only be reached from the top of the elephant (except the covenant get dropped off onto the structures), maybe with switches to gain access to warthogs or other vehicles.