I see no reason to voluntarily surrender the A plan. Union member or not, I also see no pragmatic reason to plan my life in 20 years from now around it being there. There is too much time between then and now...
The A-plan is non negotiable IMHO. The B plan is where we will need to fight like hell to hold on to what we have and increase future contributions. The looming age 60 changes give the bean counters lots of ammo to go after it.
The real way to work through all this is with some professional financial planners. I don't care if our money comes from 401ks, B plans, A plans, or "signing bonuses" every year. The point is that is comes from the company, is secure, and is under the control of the pilots to the max extent practical or monitored by a trusted third party.