As far as I know in order to reference stuff from a tool it would have to stay in the StarterCharacter
This is not true, and also a very poor practice in general. From this post:
StarterCharacter [Class Model]
All objects placed inside this model will be copied to the Character model of each Player as they join the game or respawn after death. These objects will be loaded in place of the default character that is sent from the website.
A much better idea would be to use the Player.CharacterAdded event and reference the Hinge from there (remember, you can reference a player’s character from the workspace once this event fires).
You should usually keep Tools in either ReplicatedStorage or ServerStorage and clone them to the player’s backpack when they load in to the game. If you don’t need that much control, just put the tool inside StarterPack.