I hear you, but I've never had a problem with polyphony. Generally speaking, if you are having a polyphony problem, it means your arrangement if probably too full (dirty and muddy) -- that's been my experience. My theory in mixing is less is better since it brings better clarity and punch. I've also never needed to layer more than three sounds. If you have three sounds and you don't like the way it sounds, the solution is generally to change those three sounds -- not add to them.

Out of curiosity, please tell me an example of how you would layer 10 real time parts.