i think there would be a capturable sapper everytime you destroy enemy tower - once its destroyed, you go, destroy some mine @ your base and gather gold for upgrades. That would be 'gold' and 'exp'. Exp would be unlimited (tupacs map exploit or w/e). Respawn is just creating free units with 1/1 farm level. Regeneration - trapped paladins @ home.
Could be an AI controlled 'baron' idea to capture 1 more sapper or a catapult, idk.
minions are a problem, probably one of the neutral players would be forced to create minion waves LOL