I think it's a good role. Maybe to stop it being so overpowered though, it takes either 2 nights to learn the trade, or it takes 2 nights to make an item, or it makes the item for itself.
So Gunsmith visits Apprentice N1. D1, apprentice gets message "You have been apprenticed." N2, "You have: started your apprenticeship / started crafting a gun / gets an option to give self gun" D2, Gets self gun N3, You have: completed your apprenticeship / crafted a gun. Give to who?
Just so you don't have one lucky visit N1 and all of a sudden there are guns flying everywhere.