I'm suprised that you feel the crew willfully and happily cause disruption...generally I find that c crew HATE to lose their forward roster because they have to cancel their life until it becomes stable. Not knowing when or where you are going is such a huge problem.
The quid pro quo of allowing the airline to manage the business flexibly during the disruption periods should be the ability to all crew to bid freely for lines as do crew many other airlines, and as flight crew do today.
The ability to manage work around leisure creates employee buy-in to the roster - regardless of short-term disruption, the airline would have little practical ability to rewrite rosters at short-term notice due to the vast number of people involved.
The cost of bidding would be negligible primarily due to the savings created by fewer "sickies".