Interesting question. A few parts to it.
1. Are we going to need 457s for mainline? Wouldn’t have thought so. We have a training capacity issue, not a lack of suitable pilots/ applicants issue. Qantas were warned about the training capacity issue as early as late 2013 and then multiple times through 2014 in the lead up to the 767 RIN.
2. Any 457 visa holder is likely to take just as long to recruit, train and check to line as a current pilot..... in a system that has no excess training capacity to train/check them anyway.
3. I can’t see the government approving 457s for mainline when we have plenty of applicants and plenty of pilots (currently). They’ll rightly ask why we aren’t simply promoting internally.
4. So I’m not expending too much energy jumping at shadows even if I had the spare capacity/ brain power to do so- that’s part of the reason I pay union dues.