KEF
If KEF was to happen from NCL there's really two possibilities, one is that EZY use one of the aircraft they have sitting around on certain days during the winter to start a seasonal flight to test the water, but I very much doubt they'd continue it into the summer when they can make more from the bucket and spade routes.
The second and what I think would be more viable option would be Icelandair or WOW, mainly because they can sell onward connections, I think the latter would probably be the better bet from NCL purely because of ticket price.
Not sure how much of a market there would be for cargo but I know EZY doesn't carry it and FI does, not sure about WOW.