Those are fair points, but if you add in the factor of more effective AP bombs like the OP suggested, maybe we would see a few more of the hangar queens that can carry them.
Also, how much of a factor are the 5" guns in taking down formations of level bombers? This is a honest question, I don't have much experience with the 5"-ers. My observations seem to indicate that bombers that are flying low enough to be threatened by the 5" guns are going to be torn apart by everything else, too.