(While continuing to take this thread OT)
When booking BA tickets with Avios, on the payment page, the third line "Is the payment card holder travelling on this booking?" select No.
Then, once ticketed, go to AA.com>Plan Travel>My Trips>Find Reservation (use flight #, date and departure city) then add your advantage number to that reservation.
When doing it this way I haven't had a problem with AA not recognizing my status and I assume it would be the same for free bags from Citi AA cc.