The only limitation on the weapon side of it is that the Kingdom is pre-gunpowder, so the pistol would likely be replaced with a small crossbow, and the smoke bombs would be magic based instead of anything with gunpowder. The amount is not a problem.

As for the ability, it would depend how it works! If it just labels people based on his decisions about them, that's totally fine. If it labels before he's met then, then you'd need a permission post for PCs and the upper level/named NPCs would all be just labeled as "persons of interest" until he had spoken to them and decided for himself which category they fit into.