Firestorm and Caspian are big but all of the action is centralized due to capture point placement. They can be fun but they're fundamentally flawed. Really the only stand out maps with large design that is taken into account for proper Conquest play are the old BF2 maps they just ported over. I agree that Metro is a piece of shit though, it's basically a glorified attachment unlocker. There is nothing redeeming to the design whatsoever. It just encourages the worst elements of the game like mindless explosive spamming and pointless choke camping.
Never played Arma2, any good?
Playing: Xenoblade Chronicles DE, Ys IX, God of War
Watching: Lupin, You me and the Apocalypse, Days of Thunder