Tower Defense/Offense Mix?

An idea that came to me while playing a TD Offense map DIRECTLY After playing a TD Map, was to mix the too.

Basic concept, A tic-tac-toe design, team 1,2,3,4 residing at each ends, and in the center are creep spawns, and every creep the team kills BECOMES part of the army, and you can also trade in the units you killed and gained control of for points which can be spent at a unit shop, so you can mix up your army a bit. Then, you send your army directly across the map to try to score points against the enemy team for each creep that makes it through. First team to 1/10/25/50 points loses, then last team standing wins.

When only team 1 and 2, 3 and 4, 2 and 4, 1 and 3 remain (They don't face eachother a deathround begins in the very middle square, where the army gained in the defense levels is pitted against the other team etc. and the winner takes home the victory.

Good idea or no?

too laggy. Why have creeps you kill get spawned for your opponents. So for every 1 creep you kill 3 more enter the field on your opponents side. Making this quick and *visualy entertaining* very quickly.