As far as I can tell, only players with contracts can be on your AHL team so I can't see any Cap circumvention. The only players without contracts are in your "Prospects" list and you retain their rights for two years. You either must offer a contract within the two years or risk losing them to free agency.
Once you offer them a contract (and it is accepted) they would move over to your AHL affiliate and their salary would count towards the cap.