It would probably be counter intuitive for NCL with any long term, medium/long haul aspirations, but I'd quite like to see Flybe do NCL-MAN...
MAN is bigger than ever before, embarking on ambitious new expansion and has a very very good selection of onward connections.
As I say, counter intuitive, but surely with Cathay, Virgin, Singapore and Etihad onboard, and the Avios link, there would be people who would fly to MAN for a connection. I know a lot of people that drive, or get the train to fly from MAN, well timed connections could sway people, and I'm sure NCL would be grateful to have them passing through, maybe having a drink or two, as opposed to getting the train or driving.
With short check in times, a 40 minute flight could rival the 3 hour train for some people in the North East, and could very plausibly be cheaper