Why would the brutal IR team cave into your gentle requests for improvements in the next EBA when so many continue to save the company's backside by coming into work for pittance?
You all know what a heavily delayed or cancelled charter costs them. That's not your problem. If all of you stood strong for two or three rosters and refused to work more than you're contractually required/rostered then very quickly you'd see management have a freak out and come to the table knowing they have no choice but to offer you more to come into work on your well deserved days off.
Tell them next time to cancel the flight or pay you what you're worth. The guys and girls in the 737 get a minimum FO call out of $900 and $1408 for Captain. And if it's a flight/s longer than 4 hours like a Broome return or Darwin return then that goes up even higher.
What have you got to lose to say no and ask for something similar?
Again, ask yourselves what their costs are if they cancel a flight? I'm sure someone else here can quote the rumoured figures.