The protections exist already, and they are the best kinds of protections of all, because they involve greenbacks rather than contractual terms: the company can't reduce flying across all fleets, or eliminate a senior fleet right now, at least not in a cost-effective way. That's not because the contract prevents it (they know how to get around that), but because of where the senior pilots are concentrated.

I'm sure you'd be the frst to argue NFC's are not worth the paper they're printed on, so the better protections are always financial or physical limitiations placed on the company. If they have to train everyone in huge cascade events because people are displacing to a different airplane, they have a serious incentive not to reduce/furlough without a long-term payback. I don't know what contractual protections you would wish to add, but these cannot trump the limitations that would be recognized by the company's own bean-counters.

So I think you're tired of arguing this because you've just found the perfect argument against longevity pay, and you're stuck. I hadn't even thought of it beforehand: longevity pay is the perfect way to ensure easy, smooth, economical reductions in flying.