I don't like that typical approach they be taking, whereas the defense is fine, you needed an offensive guy especially to guide and coddle Fields. You need a HC to lead the team. He, in turn, hires what he feels is the best people to work with Fields and the offense. And it's not as if a HC can't see your QB needs better protection and weapons just cause he's of a defensive background. Have to believe he has a good overall knowledge of all things football, having made a career out of it.
I don't know much else about the guy other than he was DC for the Colts. He might end up sucking and he might end up being real good. How he does is not contingent on whether he used to be a DC or OC. Has to do much more with leadership qualities, vision and molding the team into winners.