There's also a difference between toggling between two QBs because you can't decide and INTENTIONALLY playing two QBs and running plays specifically designed for the two QBs when they're in the game. The latter isn't always successful, but it certainly can be - see Florida's 2006 national title when Leak was the primary QB, but they brought in Tebow (true freshman) in regularly for specific game situations (mostly for the QB run game, which Leak was poor at).
In our case, Howard is playing poorly and, if we did that now, it'll obviously look like a move made because of that (that's why, had this coaching staff gameplanned all along with AJ, it wouldn't look that way now). Instead of taking the long view, the staff should have realized that when you have an elite talent like AJ, you get the kid on the field - even if it's only 10-15 plays a game. Screw a redshirt and 5 years - get the kid on the field.
Regardless, in my view, Will's got another 1-2 games to salvage himself as "the guy" and if he can't, burn it down and play Rubley, AJ, whomever. Because if Will plays at the level of what he played at vs. OSU, he no longer deserves to be "the guy" - the coaches will know it, the players will know it and even us dumb fans will know it.