Would a reostat work on the blower motor to give you many varying speeds in the range from off to high?
It would get VERY hot! I wouldn't try it. Current flow for a blower motor is much higher than the light bulbs it is designed for and it gets too hot to touch with that small amount of current. A variable cooling fan controller would work better or you could piece together parts from a vintage air Gen IV ac system to have a variable fan. I have some parts from a 1998 town car that I was trying to put together to make the fan variable speed since I can never get just the right amount of air.
Maybe I'll just stick to on-off LOL! This Taurus console has a nice square well, behind the shifter hole, that originally held cassettes - that is the area where I want to mount that flat mount headlight switch that I have pictured in the beginning of this thread - getting all of the switches to match and not stick way up out of the well is my goal - this is why I am trying to get that multiples of that same flat headlight switch to do different things.
If you can get the knob off of the headlight switch, you could gut the switch and replace the guts with a rotary blower switch from behind. you'd never know from the front. The rotary vacuum selector switches and blower switches for the F150s or Expedition's bolt in to the back of the HVAC panel and pass through the front. I don't know if they're the same size as the headlight switch, but they are all "D" shaped so getting knobs may not be too hard and you could make your own custom bezel.