I like my Air 2. In fact I have the BC you refer to (Pro QD+, which I like). My wife and I practiced a bit as we both went to the Air 2 setup. We were a little nervous at first, but after practicing and talking, we just understood that if either of us ran out of air, we would signal (if not totally freaked out), and grab the others primary. Obviuosly this means that we would have to go to our Air 2. By the way, I don't have any trouble breathing through my Air 2, which I did a lot of during the first few dives. Yes, you have limited head movement, but I don't think you'll be sightseeing down their in a OOA situaation. My wife actually went low on air on one of our first dives with the Air 2, and we practiced doing OOA drill the whole way back. Plus we did some practicing during the first few dives.
I recommend putting you primary on a yellow hose though. I will be. With a primary and oct, it is easy to get at least ONE reg if yours comes out of your mouth. It is a little harder to find just one, in my opinion, and a yellow hose may help you find it.