Maybe you get the reverb wash when you spend $2200 or more. Mark V, Roadster and JP-2C all have it and the common theme here is they cost more than $2200. TC-50 and RA100 do not seem to have it and they chime in at $1900 or less (head only versions).
Since the midi controller is switching everything in the JP-2C, I wonder if there are timing parameters that are used to control the reverb mute circuit. If so, you could update the firmware in the midi switcher if Mesa decides to make a fix for this problem. (this is assuming all is done by Midi since the footswitch is a midi controller too.)
One thing I have not tried yet with the JP-2C is to use the mini toggle switch to change channels. When I was checking out if the reverb wash was present on the TC-50, I did not have the footswitch plugged in and was using the mini toggle to change channels. No wash..... will have to try again with the footswitch connected. On that point, does the JP-2c do the wash without the footswitch connected and the reverb toggle in the on position. I will have to experiment this weekend if I can find the time to see if the toggle switches have the same effect as the footswitch.
If anyone is changing channels though external midi , do you get the reverb wash if the reverb is only used with CH1 and change from CH2/CH3 to CH1?