Nick,
An upgrade from an HCC/AOS to an AM/AOS on a subsequent blooming is not an impossibility. In fact, that's exactly what we did when we awarded the Paph. Tokyo Knight Dream `Ice Palace' AM/AOS in Chicago a couple of weeks ago; The plant had already received an HCC/AOS on a previous blooming and we upgraded it to an AM/AOS based on it's being superior to it's previous blooming. Theoretically, it's possible to do this with any award until the plant ultimately receives an FCC/AOS.