It will take a young person decades of full time work to save up the cash required to pay for training up front.
It doesn't take decades. Many thousands of airline pilots have simply worked and flown at the same time doing their subjects by correspondence and are airline ready by the time they are 23 with a couple of thousand hours. They also don't have the massive HECS debt hanging over their head. There is a career in aviation or there is the current self-funded cadet program. I would agree with your point about seniority number but if you are in airlines young enough then it doesn't make that much difference in the long run. If you want an airline career in Qantas mainline then you are better off applying direct from GA. Going into QLink or Jetstar from the cadet scheme is not going to give you any better seniority number in mainline. That rort stopped many years ago.