Quote:
"Well, I would assume that a single Alliance FFP would be beficial, because such benefits like upgrades would find one harmonised recognition."

This is a HUGE assumption, which if correct would certainly be an added bonus. However, given the varying demands of some 15 different marketing organizations I wouldn't ever make this assumption. Additionally, the percentage of a certain program's FF participants that take advantage of even the most basic of benefits (say redeeming your UA M+ miles for travel on another *A carrier) are relatively small (my guess as it pertains to UA M+ would be less than 2%). So for each carrier to modify their FF program to accomodate a small (but significant) group seems like a waste.