Pete, I knew you were a closet Dark Side member
As for the heater controls. I'm in the same camp as Garrett and a switch for the fan will be enough in cabin control.
Too much clutter on the dash takes away from the race car simplicity. No glove box for me either.
The Denso heater I've got has flaps on the front you open by hand to vent heat to the cabin. The rest of the time it'll just blow on the screen. To control the heat will jut be a ball valve in line tap in the engine bay (on for winter, off for summer).
You should be able to pick up on of those HQ control panels for next to nothing. I've probably got one somewhere in a box of junk in my shed.
Cheers