They are not full time and part of the proposal is to have some full time refs, but the NFLRA is not griping much about that. They seem focused on money and the additional crews.
I'm more than willing to have replacement refs if it means that the two worst crews get sat every week.
In the bargaining process, the NFL wanted something in return for the drastic increase in salary the refs wanted.
I'm not sure why anyone would be against referee accountability.