In concert I got trouble when I had to step up by two or three patches. In this case, I do not start scrolling with keeping the pedal down, I rather make single steps up. Or I want to do so, but typically I end up stepping too fast and instead of stepping up by two I rather step down by one ☹
Your idea would be a good solution for you, but I do not think that too many people would have a device to connect the FI into FX loop. I have another idea. While keeping the functionality of the ON/OFF switch unchanged, we could add a special functionality to it. When you make two quick steps on ON/OFF then it would turn off the FI for a brief moment (while you do not play anyway), and the turn on again, so nothing changed; this action could result a step down. Of course this could be done only for single step down, but anyway it can be useful. And confusion of doing step up and step down on the same pedal could be avoided.