When Utah beat Alabama, were they a "Big Guy" or a "Little Guy"?
I suspect a large majority of sports fans would say they were a little guy (and now we see them getting even smaller).
Boise State is a "little guy", BYU is a "little guy". TCU is a "little guy". Yet all of them have slain Goliath.
Sorry to burst your bubble; but one of the great draws of March Madness is seeing how far a little guy will go into the tournament. I understand football is different than basketball. Still, upsets happen and a team can get hot.
Plus a 16 team field would change the dynamic of recruiting. Another reason the big guys would be opposed to it.