While the attack decay is a cool pedal, it is analog (BBD-powered), it can be DIY-built so why buy it (Madbean has PCBs), and has nothing to do with the post.
As for your question, it's been a couple years since I played with a 9-Series pedal (I owned a B9 for about 2 weeks), they use a mechanical rotary switch for patch selection, right? I'd imagine it's a simple address selector where each position responds to an address. I'd imagine it would be fairly trivial to remove the rotary switch and connect the wires to a microcontroller to generate the high/low signals corresponding to each address.
I guess another step is if you're having multiple units in one enclosure and recalling a setting from one you'll need to bypass the ones that don't correspond to your preset. Still not terribly complicated, but you're essentially talking about making a programmable looper and digital address generator. Handful of relays and a microcontroller with a decent number of I/O and you would be set.
