Binding arbitration follows a person or group no matter who represents them. That's what makes it binding. Your union can negotiate and do whatever they think will produce the result they want, but they can not walk away from consequences of those decisions actions. If you came up with something the west can actually live with, and EVERYONE agrees to walk away from the arbitrated award, then it truly would be dead. (Or at least consensually ignored.) That's why ALPA could not walk away from it either. The west had to agree to something else, otherwise the result of the arbitration is... (here comes that word again)... binding.
As long as it followed the rules that were in place at the time both sides agreed to enter the arbitration (which it did), there is no unilateral changing of it. The Nic award was never on trial, nor will it ever be. Every step away from the nic is a risk for USAPA because it is a step closer to a ripe DFR case. You guys are in a corner unless you produce something that everyone agrees to. Not a likely outcome, still but possible. Which is why the 9th took a "wait and see what happens" approach. But if the west pilots feel harmed by USAPA, they have every right to hold on to the award and seek legal remedy since it is binding on the group.