This was a really cool concept! The pixel shader was a neat touch. I encountered several weird bugs: some buildings were not repairable and some players spawned underneath the world and were unreachable.
My suggestion to boost the gameplay even more if you build on this game further: instead of losing if all players on a team are disconnected, perhaps have a meter representing how much "fun" the players are having. If there's too many hackers, bugs and disconnected players, the fun meter deteriorates and you lose when it reaches zero.