I hate to say it but I cant see this as winnable.
The o/seas guys who will bid for Australian jobs will be Australians with Aussie passports, cant really stop that.
The new job contracts are legit and if signed by whoever will be binding. There is enough desperation in this industry to fill any jet position, look at the JQ A330 Singapore.
We are unfortunately in the age of if you dont like it leave , and there is lots more not to like coming.
JQ are one step ahead , they know maybe 50 or so F/Os will leave, cadets will fill the positions on lower salary, its a win win for the company.
I hope you guys can achieve something I really do, but it sure looks bleak.