I have not done it yet, but according to the manuals you can send midi program changes when you press on a preset. So, lets say you push a preset with Fuzz, it can send a midi signal to the BEF Pro to activate a preset all with that one press. Now most all of the multi-fx I've studied (B9,M5,M9,GT-10b) all only send midi on one channel. So one device. But, you can set multiplr SA Pro pedals to the same channel and pair up 2 fx's or 1fx and 1 set to clean. A M9 + BEF pro would take care of a lot of fx needs
edit: as a bonus, you can remap the presets on rthe BEF Pro, so the one midi channel issue really is easy to work around.
I also re-looked at that M9 manual and they are not clear on setting it up, but I know you can. A friend of mine uses a M13 to control a midi Marshall head. I will tinker with my M5 and report back