1) Stack sequencers
2) Buy some Doepfer
3) Learn Reaktor or Bidule, which is hardly stepping out-of-the-box.
The problem is MIDI is a digital protocol which means the chipbenders don't fuck with it much, but what you're looking for is pretty advanced analog behavior which means you either need to be a diehard chipbender or you need to do it in the box. In the box is so much easier.