From searching FT this seems a common topic with multiple possible solutions: (i) call BA and try to get FQTV & FQTS/FQTR set correctly; (ii) swap FFPs up to 25 hr before flight; (ii) swap FFPs shortly before boarding.

Any thoughts on pros/cons of these methods - or other methods - for this situation?

Details:
Itinerary is similar to MAN-LHR-DFW-PDX (all same day) then reverse route for return.
Booked on ba.com.
AA Plat & BAEC Blue, but switching TP/Avios collection to BAEC.

I want to:
1) earn on BAEC for TP & Avios
2) use AA Plat status to get lounge access throughout itinerary
2) use AA Plat status to preselect seats [done but don't want to lose them]
3) upgrade with Avios [no availability yet]
4) benefit from AA Plat status for AA op sectors

Is it possible to attach a different FFP to each sector?