Forget about CPI. That horse has been flogged to death since 1989.
Pilot representatives have to be aggressively directed towards forcing airlines to sufficiently resource their schedule versus the pilot service agreement.
So if the base is 70 hours, it must cost the airline significantly more to make a call out than it is to employ a pilot. What is that significant call out? Start with 2% of the base pay per day? And make any rostered time above the base hours prohibitive to encourage sufficient pilot employment.
Make it more expensive for airlines to use existing resources, than it is to employ additional resources.