@siri, thanks for sharing your ideas. They sound very interesting. If I'm understanding correctly, you'd like to have sub-zones within a current zone. i.e. Zone 2 becomes Zone 2a, 2b, 2c, etc?
Pending how many additional zones you need to add, the Doubler might be workaround for you that currently exists. I don't know if we have any users with a Doubler installed, but we'd love to test one with you if you think this would help you.