[whswhs]

Having it actually be gear isn't inherently bad. You could, after all, buy a sniper rifle as an Innate Attack with Gadget modifiers; but in a world where sniper rifles are mass produced and purchasable, you could take it as Signature Gear, or just pay cash for it. And a prosthetic arm could be any of these, depending on how readily available prosthetics are.

In fact, yet another way to describe it would be to say that you have One Arm with Mitigator. The point cost would be the point difference between having the mitigator and not having it. After all, an enemy could subdue you and detach the arm, and then you'd be handicapped till you got another one.