I really dont think it would work and the above posters have posted most of the primary reasons why it wouldnt work and why no one tried it. Nevertheless, I would be very interested to see a team like the Falcons try a 2 QB system with Vick and Schaub or any team with a pocket passer and a mobile QB.
Hard to do when Schaub is gone. Either way, in the handful of times they ran trick Vick-Schaub plays, none of them had any success. It was stupid, a tall tale sign of a desperate coaching staff who sensed their demise. Hence why it will never actually be used.
I think in theory if you had two guys like Vick you could run it from a shotgun formation. It would be very interesting, basically you would add a whole new element to the defense in that they have to guess which QB is getting it, then whether its a run or throw. This is the only way it could work though imo. Basically both guys would have to be dual threats, and able to recieve/block. It also would unnecessarily increase the chances of the guys getting hurt.