I will be flying to Australia and back later this year on a mix of BA, QF and CX. I've added the booking to BAEC but now want to credit the QF flights to my QF account. However, I will be dropping down to bronze next month so don't want to lose my selected seats.

Therefore, I plan on informing the check-in desk on arrival for the particular QF flights that I would like to change the FFP associated with that flight to my QF number. The problem arises where I have SIN-SYD-MEL with the first leg on BA and then the connecting flight on QF. Is my only option asking the check in desk in SIN to remove my BA number from the booking completely and then claiming retrospectively?

How likely is this to succeed as I have asked for my FFP number to be removed on a previous occasion at check in and my BA account was still credited. Or is it possible to credit different FFPs to my itinirary at this stage and I've just not figured out how to do it?