@Sevoris@klausman@nyrath The planetary scientist John S. Lewis, who proposed that particular gas-phase system for processing nickel-iron, emphasized that the set up would be humans inside a shell of radiation shielding well off to one side; controlling the robotic systems doing the work.
But the idea still involved hauling around spacecraft loaded with tanks of carbon monoxide (and also halogens, because halocarbonyls are a thing that can exist).