Great question. My suggestion would be to think of this as two sets of flights to be found - Australia -> Asia return and Asia - > Europe return. I’m not mentioning the Middle East due to lack of availability of Premium Economy on Etihad/Emirates - Qantas only to Dubai, but that could be an option too.
The focus for using points in Premium or Business then sits with finding the two seats from Asia to Europe and back - as worst-case scenario, you could always have a stopover and/or do the shorter flights to Asia on a paid Economy fare.
To do this, double down on Membership Rewards and consider Asia Miles or Krisflyer as the best redemption opportunities.
Break the trip down and focus on your longest flights first in terms of finding availability - in the case of Asia to Europe and back, look at Hong Kong (Cathay) or one of the many Asian cities that BA fly into as well. You could consider Malaysia Airlines but who knows what they will be up to in terms of route consolidation over the next few months.
Singapore Airlines don’t currently allow Premium Economy redemptions given they haven’t yet started flying it (I think, but it’s close) but that should come soon. Their Business class costs are also very reasonable.
Asia Miles can be redeemed for Cathay or BA Premium Economy or Business, and are usually better value than Qantas.
If you don’t think you’ll have enough points to book Business then try and research the Premium costs for Asia Miles now and as soon as you have enough points to transfer to Asia Miles, start looking for seats and lock them in.
Also consider of course booking one person in Premium and the other on a paid fare, if you won’t have enough points.
Your Virgin points won’t be much use, but Qantas may help when looking for the Brisbane -> Asia flight, and snagging an Economy redemption.
I hope that gives some pointers at least. In a nutshell:
- Keep going with Membership Rewards
- Look at Premium and Business pricing out of Asia using Asia Miles and Krisflyer
- Figure out when you’ll think you’ll have enough points to be able to start researching availability, and then go mad trying to find the right seats for your plan!