That is a fascinating thought. I wonder how many other machines work in such a manner.....
I presume Monsieur Grimm has an intake system much like the radiator of a car, except taking in fuel for power rather than air for coolant. The vents may be small, I don't know since it's a long time since I've gotten a good look at the man.
If Grimm's prosthetics work in this way, how many other machines are similarly powered? I suppose Zaul's prosthetics could be efficient so as to require relatively little fuel. This added to the usual abundance of Fog in the atmosphere might give the overseer a little more stamina than normal humans. However, it would also be poisoning his human side. I would need to know more than I do to estimate the extra stamina to poison damage ratio.
This begs the question of what exactly Fog is. Aether, as we all know, manifests when we perform acts of kindness and responsibility, caring for people and environment. If Aether manifests from acts of goodness, what if Fog manifests from acts of wickedness. The more evil that is done, the more Fog is in the air.
This ties into another theory that the gem in the Aethermeter acts as a kind of Aether magnet. A Resistor does an act of goodness, Aether manifests and is sucked into the Aethermeter to be held until released. I suspect these strange jewels originate at the Aetherswell and may even be cut from the crystals there.
Imperial subjects carry no such Fog-meter to capture and store Fog. When they perform and act of wickedness, the Fog simply drifts into the air to work its evil where it will. This, you have to admit, gives Imperial technology an inexhaustible supply of fuel. As long as they can capture Fog, they can run their machines.
If Aether is released into the air, the Fog is driven away by its presence. any Imperial technology that relies on Fog from the air eventually sputters out.
Perhaps this is how Zaul has his Road-to-Damascus moment. Aether is introduced into his system by the Scarlet Man and he is completely destroyed by it. His prosthetics cease to function, his goggles go black, the Overseer is entirely helpless. He has to be pushed around in a makeshift wheelchair, or airlifted by homing balloon.