On the grand scheme of things, while we all might get a little hot under the collar about BFS v BHD, the travel time between then is about 25 minutes. Not a huge inconvenience when travelling to a European destination.
This is why I feel that each airport should play to its strengths, and I guess their stereotypical demographic. BHD catering to the regional domestics, more business orientated flights and hopefully European cities (Germanwings, KLM, etc); and BFS operating the charters, long haul and bucket and spade loco's.
Each are a business and are out to get a good return to their shareholders, yes, but traditionally BHD was seen as the regional / business airport, and my own personal view would be a return to this would be ideal.
In regard to BA's return, WW stated his intention to get BA flying back into Belfast, long before the bmi takeover. Also when we discuss slot availability at LHR, and potential BA long hauls; NCL has I think 7 flights a day into LHR. If BA feel they get a good return on these flights, why not the same for Belfast?? If anything I'd guess the NI to LHR market would be stronger than from NCL. If demand currently warrants 3 EI and 6 BD flights a day from Belfast, maybe a small reduction could be facilitated, however I cannot see this being reduced to say only 5 or 6 EI flights from BFS. I believe that the BD BHD route was one of the most successful and a bit of a cash cow for them. Would BA walk away from that?? I'd say that BA will operate from BHD, and hopefully forge a stable relationship for the future.