Some weapons should be findable only, or require certain quest. Would add another element to the game. Edit: Didn't read any post above me so if someone said this oh well.
This would be nice not only for what you thinking of using it for but also the RPG side of the game, could also add more data to this like similar to the databook categories. Chuunin Promotion Age/TimeANBU Age/TimeAnd etc.