You know, that's a good question. I think if you gave someone like Byron Scott the warriors, it'd be bad for them. But give them a half decent coach and they're still a very good team. I think, however, to be contenders and such a dominant team, they'll need an elite coach.
Side note. I don't think Luke is that great of a coach. I mean, Kerr was still helping the warriors while Luke was coaching, he was just not on the sideline.