Well you can actually steal zone C and force the enemies to start spawning at A. Although it would be a difficult task to steal B, just make sure you go as a team when you do. Quitting will never solve the problem.

It is difficult to go 'as a team to C' when playing with randoms. I usually try to rush C. In fact, I have flipped the spawns several times by rushing through the central point and over the raised platform where snipers cover C. Hiding back there (killing anyone who finds me), and as my team dies, they re-spawn around me. I never said I quit bro. It is not in my nature. I play to the bitter end. There can be no denying that the map is unbalenced however and makes for frustrating play if spawning at A.