Probabilistic sample trigging (along the lines of both @papernoise 's suggestion and @nfim 's suggestion) was discussed:
- Tip: Randomly firing samples using silent slices
- http://www.elektron-users.com/index.php?option=com_fireboard&Itemid=28&func=view&id=228419&catid=9&limit=10&limitstart=0
What I really appreciate about the OP’s idea is that it applies in the MIDI track realm, which hadn’t been fruitfully discussed much in terms of ‘probability hacks.’