You currently allow the course builders a free hand so you are always going to have variations in levels of difficulty. The Americans use a system which accurately measures each targets distance and kill size and awards it a nominal value. If you take a cone from the firing line to a 40mm kill at 50m in theory a 25mm target placed at 25m has a similar level of difficulty.(wind/elevation is not a factor)
Yes the American Troyer system could be adopted over here, it could be used to keep courses above or below a certain difficulty level or used with a handicap system.
If the main problem to overcome is too many people in AA, then surely the suggestion of limiting the numbers in each grade is the best option? And it wouldn't need further tweeking in the future.
Anschutz 2013 MEC1 .22LR
Miroku 3800 12bore