Taking the flight that best suits your budget & schedule and treating any ff miles as bonus that may or may not be able to used is now a solid alternative to staying with a single alliance.
Once signed up for a ffp, like DL's, the amount of miles or lackthere of will be more apparent, correct?
Otherwise, I am thinking that if always flying on AS ffp partners, the best option is to book through delta.com using a Gold Delta Sky Miles AMEX. I do not plan on hitting the $4,000 90-day mark for Chase's offer.