Having worked under many different flight and duty limitations around the world I found CAO 48 the least fatiguing of them all.Of course any exemption to CAO 48 is going to be more fatiguing,that's why it's an exemption!! You work harder !!
CASA is approving all these fatigue management systems because the end game is to remove CAO 48 completely so they will not be culpable if an accident can be proven on fatigue.
Remember the CAO's are based on the CAR's which are an act of parliament and therefore a legal requirement under the laws of the land.If you break the CAO's you are breaking the law.And so are the companies who try to made you fly illegally.That is another big advantage of CAO 48.
What is the legal status of fatigue management systems? Who is responsible if "a system" is found to be fatiguing and the cause of an accident?