Braxton had to leave the QB position because his shoulder would not allow him to throw the ball any more. He was physically incapable of it.
Taysom has had 3 devastating lower leg injuries. Who knows how effective he'll be in the run game at this point. If he comes back, it has to be at the QB spot. Maybe he'll continue to improve on his accuracy and we can cross our fingers that he's at least close to being as mobile as he was prior.