DMC-6D with the universal firmware only send 2 CCs per channel on the expander port (you need to buy/build a 2-way footswitch to make it happen though).
On looper mode, I think it only sends midi note numbers.
On scrolling and presets modes it sends Program Changes.
Unfortunately, I couldn’t get the best of it with my Eventide boxes due to its limitations, it works well with the Strymon Timeline though.
I would rather get a Programmable MIDI controller instead or you might want to ask those guys to make a custom firmware where you can send some CCs.
BTW, What a great update on the whole website! Congratulations to the web devs.