Home brew afc controller

Why couldn’t a guy do all the appropriate afc mods, foot grinded, max travel spring and add some air line to the afc and an adjustable air pressure regulator in the cab. Basically afc live for cheap...
Am I wrong? Am I stepping on toes?

Regulator and a flow control (needle) valve and you have it. If you know how an afc works, you can tune it on the fly pretty well.