That's exactly what Ellison and Allinghi did in the last cup. We just don't start with the same boat they do. (Yes, I know they had them made specifically for the race.)
The origin of the AC is that I've got this big-ass fast boat, come to my waters and see if you can beat my boat. These were the fastest boats of the day. That is what the last AC was. Like it or not, the last AC was how the AC got started.
Is my understanding incorrect that in the days of the 12 meter ACs, there were some field leveling limits? I don't know this for sure, but it seems those were the glory days of viewership for the race. It seems that the public in general have voted against the current race format, since viewership was way down.