If I were to build something like this, I would have just one pot in order that the pot can be completely bypassed.
Or, I would keep two pots and
add a second footswitch in order to bypass the pot circuitry altogether.
I'd have to think about it, but the interactions of the carbon path between the topside terminal, the wiper and the ground tab could make for some funky interactions with the guitar's pot and a funny taper.
I'd have to think about it, but I'd maybe wire up the pot in a box a little differently than the usual volume pot topology. I'd want something like a single resistor that could be varied rather than two effective resistors being varied in the pedal with the conventional volume pot topology. Follow me?
This might be accomplished by wiring it so that hot is connected to the wiper and the bottomside terminal to ground.
This way, the resistance could be varied evenly. I'd also experiment with pot values and taper, linear or audio...
Just thinking out loud here.
