There will be no centralised incentive. Only the airport can incentivise the route, and they're not going to give away freebies for ever.
The BFS route benefits from Barnett's billions to the tune of £3m a year in addition to the APD concession. This will never happen in an English airport. Regardless of need. Other countries have subsidies airports and routes. I think England has one route if you ignore the route development fund routes.