Rather than, or in addition to visual gauging of engine load, how about a pedal feedback and dampening in one? A simple spring or modified throttle plate cam would never be accurate enough because throttle position and manifold pressure is relative to rpm.
Idea I had when I was asleep last night:
I imagine the success of the idea would mainly depend on the size of the vacuum tank and how well the air cylinder is sealed, along with internal friction of the air cylinder - is the break away force going to be excessive? Doubtful, as it would be a very small diameter cylinder. The rest is pretty obvious, but hopefully I haven't overlooked something painfully simple, if so maybe someone can catch it.
