As for monopolies, well if there is a market for 2 players, there would be someone else who steps up, for all the sentiments that no one would step in the shoes of VA if they go under, maybe that just means that after this crisis, there isn't enough market for more than 1 player?
Nature abhors a vacuum. IF and its a big IF QF/Jetstar found themselves in a monopoly position for a short while, say 6-12 months, then the federal government can with a stroke of a legislative pen price cap fares. Shortly after a foreign (or local) company would move into the vacuum left by VA, just like
VB did after Ansett died. I admit they already had nine aircraft up and running at that time.