Lambda Wars (formerly Half-Life 2: Wars) brings the struggle between the human resistance and their Combine overlords to a multiplayer real-time strategy setting. The Lambda Wars beta only requires Alien Swarm installed to play. It features 3 multiplayer game modes: Sandbox, Annihilation and Overrun, showcasing the Rebels and Combine playable factions and a full-fledged RTS interface and HUD. There is also a singleplayer tutorial and a handful of singleplayer missions.
The maps I've made have gradually become larger and more dense because games were not lasting long enough and there weren't enough things to do.
In older maps you would capture the 2 or 3 points on your side and that was it. If you got behind it was difficult to come back and winning by just attack moving your ball of units happened too often.
This map has 12 control points compared to the usual 6 or 7 and is almost twice as large as most current maps to make for more back and forth games.