It should be that the vest be a single-use ability as SuicidalOptimist mentioned, OR, that the blacksmith cannot give out any vests while the one he created is still active. stacking vests seems OP. Then again, maybe its just me.
Why did you make this role so powerful? If it were a single use ability, it would have been great. Then players would have to actually think about when to give the vest instead of just giving one every night.