On Sun, 12 Mar 2017 09:55:05 -0700 (PDT), trader_4
wrote:

As would an Interlockit on the panel and inlet. Looks like
the same or less work than your switch/inlet solution for
just the furnace.

Load management is the problem when you are feeding the main panel.
You may find that there is just too much on the 2 or 3 circuits you
want to enable.