I'm learning and finding things bit by bit myself.
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This sounds incredible 
I have absolutely no idea whats possible but could you potentially have a looping function? I guess primarily for live, so if you preset a tempo and loop length then it loops round recording each time so you can have a sort of additive progression.
So you might set 120bpm + 8 bars, then it will loop, so you could start with the kick, then move on to other sounds to build it up in real time. Its kind of the way I've started to use nanoloop, although with piano roll (or stave) you'd have more scope as you could in theory have a really long progression loop rather than being limited to the 16 nl grid notes.
I'm not sure how easy that would be to do with the d-pad as you might not be able to input notes fast enough (works well on nl for iphone because of the touch screen so its much faster), but if we managed to get an external controller, maybe similar to LSDJ keyboard then it would be easier? ..or even using a midi piano keyboard and an arduinoboy to control it?
I have no idea if that made sense, but yeah