Perhaps to even it out is that the device has a great deal of heat output, radiation output, something, that forces it to have it's own 'blister' on the hull so that it can efficiently remove heat from the vessel, and in the case of overheat, it won't seriously damage the ship. This way, if you trap an enemy ship, they can target that device and destroy it, without having to just blow up your ship. Then they can flee.