>Any chemical they try to add to replace the lead will require the total rework of the fuel system of every piston powered aircraft in the USA.
That is nonsense. The fuel system doesn't care if there's lead in the fuel or not. The engine only cares if the octane is sufficient, and 100 octane is overkill for many engines. There are thousands of aircraft flying today with auto fuel STCs; many of them have been running mogas for over twenty years. There are thousands more experimental aircraft running auto fuel that don't require an STC to do so.