Swapping and sector swapping is the way ahead. Can completely re-write the roster and extend or reduce trip length. All subject to FTLs. The beauty is that if its legal then it can be done, via computer and not at the whim of a person.
Just out of interest, is there an issue with overtime or is there no overtime payment with BA? We have serious limits on my outfit on swapping because of course some try to maximise overtime while others try to maximise leasure time.