In any horse breed, be it Quarter horses, shetlands, Arabians, Morgans etc. Everyone is going to have an idea of what their favorite type is. That does not mean that they are wrong or that they are creating a different breed. (even judges like different types) Even in the dog world, a working/hunting lab is going to look very different then its counterpart in the breed/show ring.
Heck, look at the Modern Sheltand verses the regular old time Shetlands. They are all Shetlands, but a world of difference in their apperance.
I was at one time, a Morgan breeder and I prefered the more modern Morgan who could win at halter as well as driving. That is not to say I did not like the old time Justin Morgan look. The University of Vermont kept more to this old time look than any other breeder, and they had some beautiful horses in the past! ( Unfortunatly, some breeders added Saddlebred to their lines, then got caught with DNA. Others added Hackney horse and did not get caught). Thank God for DNA, though we need to go out more than 16 genetic markers if we are going to keep people from cheating.
Anyway, a dog has more value if it is AKC registered and from show stock, then a backyard dog that is someones pet. If AMHA could create a "breed", and the desire of people wanting that breed, is that not a good thing?
As far as keeping papers on oversized Miniatures. Sure, that should be available, but then why would one want to breed to an overly large Mini? It is a very large expense to breed an oversized horse, wait a year to have it foal, then wait several years hoping that it does not go over. I am sure that most breeders have somewhat oversized "A" Minis, say 34" to 35". But there comes a point where they are just too large, to be worth the gamble. Also, even if their get stays under, chances are their get will produce an awful lot of over horses.