That is the kind of thing you do not do in public. If Coach DeBoer is unwilling to let Milroe play, then some story will be presented to the media to save face (and not sabotage Milroe's draft status). "Milroe is going to work with a QB whisperer," or "Milroe has opted not to play so he can concentrate on his draft status," or something like that. If Milroe is frozen out and not happy about that, he might spill the beans, however, but I doubt the school will.
But yes, I agree, if he wants to play, I'd be willing to give him his swan song. It's just an exhibition game, really. I would keep him on a short leash. If Bama is up by two scores in the 2nd quarter and has provided some spectacular plays, I'd pull him and play Ty the rest of the game.