Since the FAI rejected the proposal for 12S, I would think allowing something as germaine to aerobatic competition as a gyro would be beyond highly-unlikely! Which leaves this an AMA question. The most natural 'break' in difficulty levels between the classes to me is after Intermediate. Guys who can fly Intermediate well woudln't benefit much (-depend on) from a gyro in their competition, and should be generally pretty accomplished. Those that aren't make it a destination class. Those that are would not realize any more of a difference in difficulty stepping to Advanced than they do now. This is also probably measurable/determinable, based on the average percentage of available points earned between classes, if we had a proper database from which to pull scores.
Interesting discussion.