'GB have no "back office" ticketing/reservations dept to speak of, so its a fairly large short term expenditure'
Going to new a new reservations system would have no large short term expenditure. The main GDS suppliers only charge per booking, and that covers the costs of putting the system in. In fact they would be able to contract a lower booking cost than they get from currently from BA, so there will be a fairly large short, medium and long-term reduction in cost. It would also allow them to begin their own on-line bookings which have an even lower cost still.
As for route licences, they would not have any issues at all getting the right permissions for any of the their current destinations.
BA have been making good money out of GB in every area for years - which has been mutually good for both companies. The new MD isa former head of BA sales and BA cargo - I feel he knows what he is doing when he is moving things away from BA.