spawn a boss in middle of the battlefield which ever team does most dmg to kill wins.
another idea is to spawn random mobs in battlefields that deal out random debuffs to any real player as they go.
like a battlefield match inside a dungeon.
another idea is to spawn mobs or perhaps one boss of choice to assist each team at beginning of match (like debuff bots or boss) not like pets. ie: red team can choose sakun or icequeen etc blue team can pick their own boss to be on their side.
another idea is a speed match to which two teams have to fight through mobs to the center of the map(dungeon) and destroy a tower to win.