Hi Laura,
even if I agree with @The_Elf in principle, I find your approach interesting. However: especially the last aspect would be quite complex (the patterns would have to have a maximum selectable length of up to 17 - in practice probably more up to 32 beats, which is what is common in sequencers).
On the other hand, this is for me already performance and less DAW operation. However, I would rather do something like that with Ableton on a clip basis. Maybe MuLab 9 could be a VST solution in Cantabile in the medium term:
What I could also imagine would be the static approach that you initially described, with the ability to call ad hoc different patterns by binding. But then the question is whether this is not beyond the scope and should really be part of Cantabile.
One last impulse (and then I’ll shut up): if I want to do something more complex (also such odd patterns) is to “abuse” a percussion machine like Stylus or Nerve as a plug. This is usually very fast and you could also put such a plug in a rack and store the most used patterns as states - then they would be available on click. No idea if this fits into your workflow - just an idea.
Have fun and greetings, Volker