May i suggest both somewhat of a new mode and map. Perhaps to a large scale city, rivaling the size of Paris or London with the objective of the attackers to swarm through the streets to the capital building/citadel. It would be similar to capture the base but with certain positions through out the city, something similar to EA's battlefield and front games where taking specific areas drive the defenders back until they are finally driven to their final base and must hold the position till their timer runs out or their reinforcements are depleted.
I personally love the idea of of battling through the streets in a 17th & 18th century warfare sense. Similar to the fighting in the alleyways, streets, and rooftops like during the French Revolution.