If they could trust their members to stay with the union line i would actually take that course. Get fired, don't sign the new contract, grounding the airline in the process.
Since it takes a few months to hire a new pilot from outside that group due to legal requirements they cannot be replaced very fast, especially without trainers and line sectors to fly under supervision.
However, that requires unity, and the willingness to help each other, and somehow i do not see that. Especially with a 10 year stint as a european union rep.