Depending on how CV progresses globally (variants & all) then companies may mandate that you have to fly direct (no stopovers outside of Australia) which is what would pay for the routes.
The business case really only stacks up from the Australian perspective given the limited number of destinations at the Australian end that warrant multiple non-stop flights from Europe. European based airlines would be faced with perhaps just a single destination to serve.
For BA - perhaps just LHR, but even with stops not profitable despite several attempted revamps.
From Paris, even with stops it was not profitable for Air France.
From Frankfurt/Munich, not profitable for Lufthansa.
For a non-Australian airline it does not make sense to operate an additional aircraft type for just one route, and economics of adding NZ would look even worse considering NZ entire pop'n is around that of Melbourne or Sydney's alone.
If no CV impact in 3 or 4 years time (vaccines handle everything with zero issues
) then economics may not stack up for Q if enough of Q's previous supporters remember how Q left them high & dry after June 8th, 2020, wouldn't refund their money (until ACCC finally intervened etc etc) & more recent issues (JQ saying Melb impending lockdown did not make fare refundable nor travel credit'able - happened to us with a 4 day Melb booking due to fly to Melb on that Thursday 2 weeks ago). Eventually after FB exposure JQ changed their mind.
Zero issue with the hotel - they immediately offered full refund when we rang on the Wednesday morning.