Leave the damage the same for body/headshots but give the fel a small aoe of reduced damage. To balance this could have mag size reduced or slightly lower firerate.
This way it can be shot at an auras feet and slightly damage her and her healing station as an example. Will be less punishing if you miss a shot, or ability to hurt/kill low health mercs that your team has damaged, or in the event the opposing team is diffusing and they have multiple proxies.