I want to turn on the defroster with a rocker switch. Does anyone know how to wire something like this?

 

You'd need a DPST switch - one circuit to power the fan circuit and one top power the A/C compressor. Of course, the vacuum for the duct campers needs to be dumped, but that is done by the ported vacuum selector switch on the function lever, and not any electrical switch. If you wanted to operate the entire HVAC system with switches and eliminate the function lever, you would need several vacuum solenoids and more switches - somewhat like what the factory did in Cadillacs.