According to this pdf file from the KHSAA, there are 217 football-playing schools in the 4 classes (54 in each class). 6 classes would be 36 or so in each class if they are broken down the same way.
I don't know any of the details of this 6-class proposal, this is the first I've heard of it. But we already have 32 out of 54 teams in each class making the playoffs (16 per semi-state, 2 semi-states per class...right?). If we spread the classes thinner & keep the same semi-state setups, it will be like the NHL where everyone makes the playoffs & marginalizes the regular season.
Personally, I think 5 classes would be pushing it. I'm with westsider's opinion that 6 would be ridiculous.