The thing is, if someone out and says they're the blacksmith and is immune to night attacks, then I'd be inclined to believe them. At that point, you either lynch the guy that's producing shields for the village or you leave him be and potentially spare a wolf. I think the wizards being able to tell the wolven or not wolven in a good idea. Because otherwise, there's absolutely no way to really tell if he's a wolf or not except by miticulously picking through his statements. If I was a wolven blacksmith, I'd abandon my bretheren and just go villager. We'd still win in the end because to all onlookers I'm a villager. I'd be the pied piper, leading the village to their inevitable doom, immune to all but lynch, and I'll have enough trusting followers to be able to survive any threats on my life. If a wolf gets wagoned, I'll be the first to hop on. If the wizards can tell the wolven trait, then as soon as I reveal as the invulnerable blacksmith, a wizard could scan me and see wolf, and my reign is over before it begins.