Companies that have hammered out an effective cost/production/time ratio are not something you can compete with without becoming the same thing as them. Which is why factory managers are literally afraid to turn them off for any reason.
My brother constantly tells me about how when they do repairs they will see something within 1-3 months of failing and tell the factory manager. He said almost without exception they always ask will it increase the repair time "TODAY" and of course the answer is yes. They always decline and deal with it when it breaks at a greater time/cost. I think this is more an effect of the toxic work relationship that has become forced on everyone by MBA's.
Where was this provided? I didn't see you or any poster provide claim or evidence that Toyota or Ford intentionally leave unused production capacity. I had a busy day so I may have missed it somewhere.
Far as I'm aware they also run their assembly as close to 99.999% of the time as possible.
My brother is not a mft. He works for an engineering company that makes and maintains manufacturing equipment. He has worked in nearly every major company you can name's manufacturing plants fixing their stuff or installing new stuff. Its a whole world I did not know about until he started. I'm just forwarding some stories he tells. Not sure why you think you know more than all the people involved.