It would be nonfunctional on arrival. It would be fixable, but your character would have to find someone with the knowledge of how to fix it. If your character would know how to fix it, then all it would take is finding someone who can take instruction to do it for your character. Daidara would likely be your best bet, because once he knows how the weapon functions, he could potentially upgrade it as well.

There's also the option of getting a new weapon entirely, but that would be up to the character and player.

Historical figures built up as legendary figures would be possible as Personae and are acceptable, so go right ahead!