I haven’t found this option besides routing every sound to a separate channel inside my DAW and then just controlling the DAW with the knobs and faders. So basically this has nothing to do with AD2 directly… it depends on how you can control your DAW with a midi controller.
Although I haven’t tried this myself with a drum library, I’m guessing you can use touchosc, which is an iOS app that is fully configurable to turn an iPad or iPhone into a midi controller.
You can configure it to send pretty much any MIDI information and is velocity sensitive and (depending on your tablet or phone) also aftertouch sensitive.
I’ve used it to send CC and key switch information with my left hand while playing a part on a keyboard with my right.
Basically, you could send whatever CC, key switch or note MIDI you wanted to AD (or your DAW) as you play.
You can make templates to configure whatever key switch toggles, dials, faders, buttons, etc. you like.