Overall, I agree. Trip costs will be similar, although the A319 should burn slightly less fuel because of lower weight. AA is proposing a mild B scale for the flight deck but without a B scale for the three FAs, these just wouldn't make all that much sense. Of course, if AA sees some FA retirements, the A319s should be staffed primarily with new-hires and their first few years is basically a B scale compared with their topped out pay.
You've pointed out before the absurdity of jetBlue flying 190s that seat just 2/3 as many passengers as their A320s yet paying the pilots 85% to 90% of the A320 payrates. And since the day B6 announced its mistake of adding the 190s, it's been basically break-even instead of the profits that preceded the 190 orders.
Only advantage to the A319 is that it can reliably fly thin transcons where the A320 and A321 fall short and need those winter fuel stops. If A319s and 73Gs make sense now, they would have made more sense several years ago - so why the sudden desire to fly higher CASM small mainline jets?
Fuel costs. Until fuel skyrocketed a couple of years ago, AA could make money or at least come close to break even flying around paid for MD80s with higher fuel consumption.