I am very happy with my install. The area too the far right is perfect for the duel cage Jegs unit. Was out yesterday in 30f temps. The three outlet directional kit was a welcome addition along with the 3 speed fan.
I have the factory single speed heater, also added a diesel heater in back for the really cold days.
I like your idea of the 3 speed resistor switch, I’ll have to get one.