The assumption that isDon is making is that the system works as it should. In that you can make a big call and cancel a flight and the union, company procedures, and the regulator etc will back you up. Companies and the regulator are interested in nothing else other than covering their arse. Don't forget too the whole fatigue issue was dealt with last time by the imfamous 'toughen up princesses' response.
It is up to the Regulator to regulate, and from what I have seen they do not have the guts to take it on.
The other problem with fatigue issues is that companies can wheel out the whole 'illegal industrial action' routine. Given that it is such a fickled issue its very difficult to deal with as an individual