Re: What happens if the pilots in each cockpit decide to bank in opposite directions?
I assume you're thinking of both pilots moving their wing down (or up) at the same time. It's definitely amusing to imagine the airplane flexing up or down in a U shape! Reality is less interesting, since that would lift or lower both wings at once and the plane would simply rise or sink.
Nevertheless, I'm having fun imagining the plane flexing around into interesting shapes as two pilots struggle for control. If they got into an oscillation loop fighting each other, you might see the wings actually flapping up and down as it flew, wouldn't that be a sight to tell your grandkids about?