Is Australia likely to be the aggressor in a future conflict? If not, then why does the RAAF need stealth?
I guess if there is an invader, it would be good to be able to engage the attack aircraft they send without being detected. And should they manage to land, it would be nice to be able to engage ground targets without their fighters taking ours out.
That said: the whole notion of Australia being invaded by anyone is just laughable. The only ones that would be able to pull it off are not going to be deterred by a hundred F-35s.
I reckon we save the money (and that for the subs) and build ourselves a nice fibre optic broadband network instead!