Suppose a furloughed pilot could "bump in" at another carrier. Wouldn't that stagnate or even displace the junior guys who were already there? What if he wasn't furloughed, but just decided to make a lateral move to a better job? If he came in at the bottom for seniority purposes but kept his old pay rate, wouldn't that be a "reverse B-scale", with senior pilots making less than juniors in the same seat?

Like "age 65", the NSL would probably be accepted if it were in place when everyone started flying -- it's the transition in mid-career that will cause problems.