implies roster instability
What are you talking about? Someone here is getting the wrong end of the stick, which one of us is it?
The question asked about rostered flight duties followed by standby. Some days I'm rostered for a 12 hour day from report to finishing the paper work. Other days I'm rostered for a couple of hours flying, then on standby for two or three hours. If I get called for a flight then I go flying (obviously as long as it's within FDP etc.) If I don't get called by the end of the rostered standby I go home. No different from any other days flying or standby.
What exactly is the problem with that?