Interesting thought. However the two effects of AMT in what you propose would be mixed, but at the same time semantically unrelated. Technically no problem, but probably not a good fit into the master model.
I do have an idea of how to add rests to the chord pool, will let you know how that goes as soon as I get my hands on a prototype.
Step GRV is already in use, but nothing against a refinement, as always 