Fatigue - a suggestion
As a mere PPL my problem is the opposite one to yours - I'm not getting enough hours!
But I have a suggestion -
Would it be possible for a few shorthaul pilots to be given tests for alertness / reaction time / other symptoms by a suitably qualified medical person, between multiple sectors? I appreciate that airlines would not cooperate in this but with a bit of subterfuge it ought to be possible, certainly after the last sector of a long day.
A peer-reviewed study of results, published in a medical journal would have to be taken seriously.
Just a thought...