I am not sure what brought about "6A", though I am sure it involved whining. The problem is, it does not work for the Western Part of the state.
What brought it about was the gigantic disparity between the largest and the smallest 5A schools. You could have combined together three of the smaller 5As and still not have been as big as the biggest 5As. And a lot of people didn't think that was fair.
The solution, if you think that this is a problem that needs to be solved, is one that the WPIAL considered and rejected. And that is to combine the 5A and the 6A schools together for football. Instead of five 6As (and only because Central Catholic is playing up) and 18 5As just combine them together into one division of 23 schools.
I mean NA already plays Baldwin and Norwin and Penn Trafford, they just aren't section games. Seneca already plays Penn Hills and Peters and Pine Richland and Hempfield and North Hills, they just aren't section games.
Make three sections, one North, one East and one South. Split the teams up as equitably as possible. And when the time comes for the playoffs you have two choices. Either one big tournament with all the schools and the 6A state playoff team is the highest finishing 6A team and the 5A state playoff team is the highest finishing 5A team. Or split them back apart for the playoffs only and run two separate brackets.
But they considered that and decided that the current way was the better choice.