FV-30H Expression Switch Mod

[FoxtrotVR]

Hey all, new member of the forums here and very new member of the modding community. I know very little about designing circuits but I do have a very primitive knowledge of soldering and circuits as I have made one or two custom cabs and even helped/looked over the shoulder of a person who was making their own custom tele as they were putting together the electronics. Anyway, I'm designing a board and I am thinking of modding my Boss FV-30H Volume pedal to take an expression input and adding a switch to go between volume and expression for a Boss MD-200. I love my FV-30H and would love to be able to switch it to an expression pedal to save space on my board and also dip my toe into modding. While researching if this was something that already existed, I came across this guys pedal from Shnobel which was similar to what I wanted if I had a pedal that was compatible with this pedal. (https://www.youtube.com/watch?v=P5iNRnXpDYQ) But not only do I not really have room for it on my board, I also don't want to have to take up another spot on my power supply. So I got this crazy idea in my head that I could do it myself.

Then that got me thinking maybe I can just mod it directly into my volume pedal. So here goes. Obviously first step is to rip out all the og electronics except the pot and the 1/4" TS input and output. The tuner output I can just replace with a 1/4" TRS input for the expression function (less holes to drill). From there things get fuzzy... I'm thinking a toggle switch on the side but I'm not sure the best way to do it.  Another feature of the above mentioned pedal from Shnobel was that when the pedal is in volume mode the expression is set to the lowest setting, and that's no fun, so I also want to add a pot to set the expression value when the pedal is in volume mode. I've drawn up some circuits that I think might work but like I said, I'm no electrical engineer.. Pot A is the main pot on the pedal, pot B is the aforementioned pot to set expression when in volume mode.

Circuit A:



Circuit B:




I have absolutely no idea if either of these would actually work hence why I'm posting here. I have much more confidence in Circuit A for obvious ground related reasons, but also for obvious switch related reasons Circuit B is favorable. If Cicuit B is plausible then I can just use a 4pdt switch which, you know, exists. While with Circuit A I would need to find a 7pdt or something similar that might be able to handle what I want to do. Like I said, I want to keep it passive so I don't have to take another slot on my power supply. And I'd rather keep it to one switch to avoid other issues that would come with having two switches.

So here's the question: Does Circuit B Work? if not, does a 7pdt toggle switch exist? (theoretically an 8 could work too if that's more plausible than a 7) If neither of these circuits are realistic then does anyone have any suggestions as to what might work for what I'm trying to do.

Thanks to anyone of decides to help me out with this, I hope my crude diagrams are clear enough for you.