I do not know where you work and what work rules are programmed into the PBS system you are using.
You are here in strong support of PBS, why?
I have also worked with PBS at a company with far superior rules and compliance than Spirit management will ever have under "Bob".
For the top 15% life is good.
20-60% gets some of their requests some of the time,
Below 70% might as well not bid, you get the leftovers and maybe ONE of your top requests.
You have a better chance of getting your choices on a relief than you do below 70% at PBS.
A union controlled PBS, with ALL the current work rules, would still be a huge concession with no turning back.

I think this is an issue of long term vs short term career goals at Spirit.
For those who plan to be here more than 5 years, PBS will motivate them to leave even sooner!