If he does start, I don't think he's the type that would play scared. I agree that there would be growing pains and some tough losses.
I was fortunate last week to run into a former BYU QB at work. I won't say who, but you'd all recognize his name. After thanking him for playing at BYU, I asked him if he'd seen Wilson play and what he thought of him.
He had been to some practices. He was very impressed with Wilson. He did say that he thought Mangum should start as he felt the two were pretty close overall. Kind of go with your senior leader type thinking.
That being said, I have no problem with Wilson starting if he has truly beaten Mangum out for the position.