you are best to hack a controller with a POT or analog dial in it already, then the controller has driver already too, as soon as you talk about new controls you are talking about new drivers and instruction sets, im not sure, but fear pulsing may get choppy
so yes, its more complicated than that, also i dont think the guy in video made that foot pedal, those pedals come with the wheel, i think what he did do was added that little spinning thing in the middle:
**broken link removed**
easiest to go just spend the 100$
what you could also do is if you have access to the footpedals and scope you could trace signal going in to the wheel, then you could spin your circuit off that, cos we dont know if pedals sends analog signal, or analog signal encrypted in digital words