I'm not sure Andrewm, I have only been flying out of NCL over the last year or so.
Just when I was there, I thought it ticked a fair few of the boxes required to sustain decent loads. Especially compared to the seemingly successful BRU flights.
Problem is of course, who could operate it. The market for connections requires high-frequency with LH, whereas the leisure market requires low fares that I doubt LH could offer on a CRJ or similar...
Either way, its a huge hole in the network, there are only seasonal Innsbruck flights that go anywhere near southern Germany!
RTG!