This whole discussion feels like it's going on in a parallel dimension. Heavy metal going into the capital cities up until 8 odd weeks ago, how many were really doing an RNAV approach vs an ILS or even a VOR/NDB approach. I don't think the situation has changed that much from that perspective surely. I suppose in the chance we have an eastern USA style blizzard, GPS goes down and so does primary and secondary radar then heavy metal may be declaring an emergency but otherwise I can't see that happening really.
For GA aircraft, all bar Archerfield have some sort of aid in the BNN, and whilst archerfield doesn't, Sunny coast and gold coast both do, so hopefully they would be able to handle some of the GA aircraft that are stuck in the blizzard.
Proximity to aids for training is a different matter altogether.