I am against an NSL and there is no way I think you could figure out how to do it. And even if ALPA national created one, it better give me the option to opt out.
As to whats killing the airline profession? The evolution of the industry. Demand created growth which created competition which was aided by technology which created replacements. I think that goes for all levels of the industry and any artificial means to overcome or control that by would be short sighted, counterproductive and naive.
I'll digress for a moment, imho one of the major missteps in this evolution was that of the "paying their dues" attitude towards regional pilots. A Delta pilot was telling me back in the early 1990s he was talking to a 1900 pilot who was getting $12,000 a year, horrific working conditions and of course PFT. The Delta pilot decided something had to be done so he went to ALPA to complain and plead to them that this was not right and the union's response was "they need to pay their dues just like we (the pilot complaining included) did in the military." Or so he says, and i kind of believe him.
The only problem for "thats what they deserve" crowd was the small turbofan was right around the corner and the Brasilia became the ERJ-145 that outright funded the E-jets, the Challenger 600 became the CRJ-100 which grew to the CRJ-900, and the Saabs, 1900s, 120s, ATRs, Jetstreams withered on the vine. And the pay stayed at "paying their dues wages."
I don't see an NSL being a solution in any shape or form. It'd be like setting fire to your boat to help you see through the fog. Let nature take its course and in the interim just make sure pilots above, with and below you are treated fairly.