AA subsidized the small jets because they added "feed" to the mainline. If the divested AE has to stand on its own and bid, at a profitable price, with 37 to 50 seat RJs they might be "underwater" pretty quickly. It's hard to make money on small jets if you are not getting a premium price. AA is not divesting AE to increase their costs--TAKE THAT TO THE BANK.
Take the AE offer? Up to you, but this business can change on a dime.
GF