You're missing the point. No one is saying Qantas should violate the EBA*. But the situation simply shouldn't exist in the first place. People in this thread are sugggesting:
* Qantas should operate in a manner such that this is an extremely rare situation; i.e. having enough standby pilots in all major ports, planning most deadhead moves well in advance
* If there is no alternative, Qantas must come up with fairer ways such as voluntary downgrades for market based compensation (i.e. keep increasing the compensation until
even Donald Trump would take it.)
* Qantas should try to renegotiate the EBA to make the right to business class less strict on short-haul flights (I understand not all would agree, but it's an option), given it's unlikely to actually be a "safety issue."
* Australia should implement fairer compensation schemes for all such issues, along the lines of US DOT's denied boarding rules or EU 261. This is the real crux of the matter.
* I would also wonder if the EBA is quite as strict as people are making it out to be. What is the actual contractual remedy if Qantas is forced to fly a deadhead pilot in Economy class? It's not like someone's going to gaol for a "violation of federal law." I suspect the actual impact will might well be elsewhere, i.e. the deadheading flight in economy might count as paid duty time rather than rest time or something like that.