Interesting discussion. CASA rules and therefore Qantas fuel policy is more conservative than other regulatory agencies I have operated with..
Like most other countries, CASA rules do not require fuel for an alternate unless the destination forecast weather conditions are below the alternate minima at the flight planning stage.
If anytime after the flight planning stage the weather conditions deteriorate below the alternate requirements or special alternate requirements, where available, the minimum inflight fuel must include fuel to an alternate.
If the inflight fuel remaining is not sufficient to enable the aircraft to conduct the approach at the destination and proceed to an alternate, then the flight must proceed to a new destination airfield that does itself not require an alternate or if it does require an alternate, the minimum inflight fuel must cover this.
In the event that the above option is not available the crew must make a decision based on the safest course of action, and file the appropriate paperwork as this is a reportable incident.
All international flights, I have operated into Sydney or any other Australian airports, that depart with flight plan fuel and no destination alternate fuel, will always have the inflight fuel on-board to divert to another suitable airport before descent has commenced.
So if forecast or actual weather conditions deteriorate below special alternate minima, inflight, and I do not have fuel to fly, approach, missed approach and full divert, then I divert to new destination.
This is Qantas fuel policy and CASA rules.
Neither the Qantas fuel policy or the CASA rules permit an aircraft to continue to a destination airport that has weather conditions below the inflight special alternate minima, let alone an airport that is below the landing minima without having full divert full to a suitable alternate.
So in answer to the opening of this thread, no I do not think there should be a change in the Qantas "Fuel Policy"
P.S
I have also operated into New Zealand ports and their rules only require the "TOD alternate" for International flights operating to a airport with a single runway, this is not a weather requirement, their alternate requirements are very similar to CASA, however the New Zealand NZCAR's "inflight fuel" only requires alternate fuel if the destination weather deteriorates below the approach minima, unlike the CASA requirement of the special alternate minima, therefore CASA rules are more conservative in this regard.
Safe Flying