Pretty sure spawns aren't decided on which zones are captured, but rather where people are. It's OK to send one person over and cap A (if you've lost all your zones), but 2 people need to not cap C and head to the back corner of C. Those two keep their spawn locked at C, while the others cap C and then work on B. Tl;dr: Capping A isn't a bad thing if you can get people in C's back corner to keep the spawn on C side.