I just don't see any of the registries supporting the "partial registration periods" that would be required to allow for syncronized registrations. If you wanted to offer this to your customers, I suspect you would have to provide them with renewal notices yourself at a particular time they want to renew all their domains, however the expiration dates would be some time in the future - not synced to these renewal notices.
What motivation would the registries have to support partial period domain registrations? I know if I were running the CNO registry, I wouldn't even consider this - as there is nothing in it for me as the registry. There are plenty of other things I would spend my money on... -t
