I think this is a great idea.
While building my first pedalboards in the MOD, I realized I needed more footswitches than the two provided by the MOD Duo itself. At first I tried working it out with the switchbox, allowing me to make three different sounds from clean / crunch / distortion. But didn’t quite cut it.
I stumbled upon the iCon G-Board, which does work. Only problem is that the LEDs on it doesn’t turn on when a footswitch is engaged. Seems to be a problem with the software within the iCon. (If anyone else tries it out and manages to work this problem out, let me know 
)
I also use an Akai MPK Mini. By using a USB-splitter I could connect both of them to the USB-port in the back of the MOD Duo and therefore have one pedalboard where I could control 10 different effects for my guitar, and at the same time use 4 different simulators for the Akai. Another awesome thing was that the Akai has 8 knobs and 8 pads, all which can be assigned any parameter. Useful to not have to scroll through it all on the knobs on the MOD.
Really cranked the CPU with that board, but did work 
TLDR; iCon G-board (OK, LEDs not working properly) and Akai MPK Mini (Works awesome)