I am not so sure they won't find pilots for mainline. It wasn't a problem when recruitment opened in 2013 on a terrible pay. There is more to it than roster and pay. Proximity to friends amd family, particularly relevant when about to start a family. Some Scandis find themselves home abroad, many come home when the opportunity arise.
As for Norwegian, I believe SK Norway has seen quite a few people leave to NAS. Wasn't it in large for getting based closer to home? While there's been plenty of talk I really only know one in SK Sweden that has gone over. And that's stuff that usually spreads like wildfire.