Larry, by posting this you raise a question. What is the code-compliant way of doing this? My imagination is tending towards the following:
Panel->Breaker->Contactor(Separate Enclosure)->Second Subpanel->Final Breakers
Although Non Code Compliant, I (at the risk of being yelled at) agree that sometimes In circumstances like this, professionals know when it is safe to break the rules.
I would agree this would be a bad idea if it were the *Main* panel, but being a subpanel it can be isolated for service by turning off the feed breaker in the main.
And with reference to your 'Stack O Outlets', EXCELLENT work, neat, and shows that such a thing can be neat and workmanlike.
