I am still curious about this topic, since almost everything is "there" except for the triggering (which is my big interest). I have not done much with MIDI, so know there are a lot of tricks out there that I do not even know about.
The Matrix view does very much allow for MIDI trigger assignments, and using the "random patterns" in a row will make them all mutually exclusive. So if I chose 4 patterns, and assigned 4 MIDI notes to trigger each, is there a way to "randomly generate" which of the 4 notes is being played as the trigger (and limit the notes being randomized)?
The only thing that comes to mind is having a silent MIDI track running with the arpeggitor enabled, but there may be a much simpler solution to random note generation (real time).