This is likely a Rule Proposal that needs written up but i'll post it here for feedback.
It is noted that you are not able to show at the Select World Show and the Amateur/Open World Show. You have to choose one or the other if you qualify for both. Also, you are unable to show the Level 1 Select Amateur and the Level 1 Amateur Class at the Level 1 Championships
With that being said I think it reasonable that there should be no cross entry within the Amateur and Select Amateur classes at AQHA Approved Shows. There are many instances of rules like this that prohibit cross entering such as Walk/Trot Exhibitors cannot enter a Lope/Canter Class and Youth cannot show Amateur.
A Select Amateur should not be allowed to show Amateur in the same version of the class at the same show but all should be Eligible for Open Classes as it is today. If the numbers do not support the Select Amateur class then combining as they always do to make a pointed class seems reasonable. However, if both are available the exhibitor should have to choose 1 or the other.
This should be done on a Class by Class basis and not a Select Versus Amateur for the entire show. The Exhibitor should be allowed to go back and forth between Select and Amateur version of the class on a show by show basis.