Sick leave is a bit of a furphy for pilots anyway.
Pilots are legally obliged to determine that they are fit to fly prior to commencing a duty. If they are not fit to fly they are subsequently required to withhold themselves from duty. If a pilot were to use more than 25 days sick leave to ensure their compliance with the CARs, and had appropriate documentary evidence, it would be an interesting exercise to see whether the requirements of the determination or the CARs took precedence.