Here. There’s a youtube link in his comment that demonstrates proof of work.
I wouldn’t do that. I’d be more inclined to drill a hole in the side and mount a 1/4" TRS jack to accommodate use of a standard footswitch, or you can use a wiring grommet to insulate the sharp edge and then use a hardwired cable going straight to the footswitch which is probably what the guy in the link did and might be necessary to address multiple buttons.
The button operation is not impacted, the button still functions as normal. The pedal connection to the button’s solder pads would be via the rear of the PCB. The biggest issue is if it needed some kind of physical components for debouncing the behavior of the additional switch but if this guy did it with play control without debouncing then I don’t see there being an issue doing the same thing with a different button.
Again, if this is to be done I would get in touch with someone who can properly test the behavior of the factory installed switches, will properly wire and install and will guarantee their work, but I do believe it’s possible to modify the machine for this purpose.
The func button would be a particularly useful switch to have on foot control. Or the fill switch, for example. It’s a bit excessive to imagine, but one could probably even do a bank of 16 footswitches with one to represent each trig, but at that point one might as well just find a more compatible instrument.