Even Kirby mentioned that Airways/AA could save 10's of millions of dollars having regional airlines doing some of their flying. The money is there. Just how we get it is the question.

And to comment on your statement about Mainline carrying more passengers...
True, but it will always be cheaper to put 40 passengers on a 50 seat jet than a 70.
And 65 on a 70 rather than a 90.....
You cannot fill a A380 from FAY to CLT.