Oh man, Falcon in split screen was such an awesome vehicle. I remember how my friend would be a gunner and i'd pilot it (with Warthogs, i was the gunner and he drove).
The secondary gunner is irrelevant, because effective flying usually presented only one side for enemies.
As long as we could prevent enemies from using lasers and rockets, we could dominate the battlefield pretty well (assuming enemy sniper or DMR guys didn't wise up).
Sure, the Falcon requires a lot of coordination but that's fine, if they can do that, they deserve it. For maps with Falcons, there could be a specialized anti-air power weapon, would make a good objective for both sides if there are good fliers.
That said, moving the gunner to a bubble turret in the front might be a good idea, make it a bit easier to use for poorly coordinated crew. But if so, i'd add some cargo/passenger room in the rear so that the aircraft would be like a miniature Hind or Pelican. Give the pilot an ability to lift a Mongoose or Ghost...