There appears to be a misalignment of incentives in this industry.
Case A: If pilots are paid variable flight pay, then pilots themselves are driven to maximise their availability. If pilots think that they won't get caught, or perhaps feel that their sickness is subjectively borderline, they are incentivised to take a chance. The employer or regulator has very little chance of controlling this type of behaviour. Other pilots, cabin crew and passengers also fall victim to the self-centred decisions of others if they catch diseases.
Case B: If pilots were paid a flat rate, then it's up to the employer to maximise their pilot utilisation within a given availability or flight time limitation scheme. The pilot on the other hand, has no conflict of interest when faced with a safety decision when sick. It would be squarely in the employer's interest to seek an explanation from the pilot who, in turn, would then be inclined to visit a medical examiner to objectively evaluate their fitness to fly.
Of course, companies would prefer case A, where pilots are paid less when not used efficiently. Regulators should take a good look at what's in the best interests of the flying public - it could be win-win for everyone except scheduling and recruitment departments. What am I missing here, any thoughts?