How do you make a Characters Arm Visible with CurrentCamera set to FirstPersonLocked?

This is a common question, and the easiest way to do it is to Weld a copy of their arms in a "local" model that only they can see that isn't a part of the their Character model.

To get the appearance right, you'll have to create a "local" Model, and give it a Humanoid, a copy of the Player's Shirt if they have one, and any modification done to the play would have to be done to the local arms as well.