I looked at the response, and I think it makes sense, but it does seem like we did this.
Let's back up a second. Since I don't have this pedal, I have to ask stupid questions, sorry. Forget CC commands for a second. When you send PC commands telling the pedal to go to specific presets, it works right? If yes....explain how the pedal works if you don't mind. When you create "Preset 1" on the Boss, do you choose what side A does and what side B does and then save that into Preset 1 in the pedal? (I understand that you're not ever using both sides...but I'm just talking here). Then you create Preset 2 in the Boss and do the same?
I guess what I'm getting at is this...if you are creating different sounds on the Boss, saving them to various presets that you can pull up with the PC commands via the PBC...then why can't you do this. Create all your sounds (however many that is). Then create 1 that is completely blank...for conversation sake, make it preset 99....as in, you get to it by sending a PC command of 99 to the Boss. Create that preset such that the pedal is still on (either the A or B side, however you saved it) but the mix or whatever is adjusted such that it does NOT sound different than the pedal being bypassed. Is this possible?
If yes, then you can forget all this CC nonsense and just make the MD500 go to Preset 99 anytime you want it off and go to something else if you don't. All you would be using is PC commands and you could delete all this junk. (Although curiosity still has me wanting to know how it works, haha).