I've made a similar proposal for Amateur AND Youth. I was going to wait til later in the year to submit it. What it would do is give shows the option of either using the class as is (Sr. and Jr. horses together) or splitting by horse age (Sr. Geldings, Jr. Geldings, Sr. Mares, Jr. Mares, etc)
Shows wouldn't be required to split the classes, but this would give them the option to. When I asked the show office, they said splitting between Jr. and Sr. wasn't allowed, even if show management wanted to do it and the show could support it.
My main push for it would be so that Jr. and Sr. horses don't have to be judged against each other and it would allow us (amateurs) to be able to show more horses.
I don't see what it would hurt allowing the option.