We have booked our BA 241 reward outward flights and are awaiting the 355 day window to open so we can book the return.

I understand that we can call BAEC and have the return leg added to the existing 241 booking.

Its a long story but is there any possibility of booking the return (using normal number of avios) via ba.com and then calling BAEC to add those flights to the original 241 booking at a later date with avios/tax recalculation?

Its a long shot I know but would be grateful for your views.