Something like this would not only be the best for fans, but it would also be the most profitable model. Maximizing eyeballs and there would be very few programs with a legitimate gripe that they got left out.
A 40 team model would to a shit ton of lawsuits and basic apathy from the 30ish fanbases that would get left out in favor of 20ish schools that are basically on the same tier as they are. That would draw worse ratings than the modern iteration, I suspect.
I still think if you're trying to get more exclusive, then you get extremely exclusive and put the 16-20 schools that are actually capable of winning a national title in the current system in their own division, and the back half of that 40 team model join up with teams 70-40 for a 50ish team level. I think this would eventually be more appealing to the back half of the 40 team model, which will really have nothing other than saying they made the cut to hang their hats on. They will never be competitive in that setting, and a lot of those fanbases will get apathetic from mounting losses. Then you have the Iowa States, Oklahoma States of the world raising holy hell.
All of a sudden a school like Arkansas or Iowa goes from being the whipping boy in a 40 team model to being a national title contender at the next level. And the 16-20ish team top tier would probably have a lot of parity, and those fanbases will be given exclusively blue blood-ish slates.
Either make the top tent a fairly inclusive thing where most of the schools know they have little shot of competing, but they're happy to be in the ring, or make it fucking tiny and only composed of those with a shot to win it.