Looks like a fun trip. Just a few pointers I can think of. Look at departing OSL as well, that's often the cheapest in Europe, I hadn't heard that BUD is now cheaper but could be wrong.

The surcharges seem to depend on which airline plates the ticket. I have a 6 QR segments on a current DONE5 and my surcharges were very low, it's QF issued. Having said that if you go QF issued, book via a travel agent, QF's customer service line for changes is mostly clueless about RTWs. I don't have any BA segments on my ticket to have tested it, but I did hear that IB segments have much lower surcharges than BA. I think both are equally as bad in business class, but just saw that the IB flight attendants sued the airline over carry on weights because they don't want to lift the larger bins on the A350 so apparently the airline will be strictly enforcing weight from now on, if that matters to you.

Agree, HNL-SYD is going to be extremely difficult, if you go LAX instead you have 2 QF flights (currently) and an AA flight, in addition to the QF BNE and MEL flights. I suspect by the time of your trip all QF LAX flights will be back on A380s again so more seats, and hopefully more D space. QF is very stingy with D space on North America flights, but AA not so much. You can always ticket it on AA72 and change it to QF later if D space opens.

For a frequent flyer plan, it's hard to say for 2024 right now as things change fast, but with BA and IB going revenue based, those may not be the best answers, depends on how they deal with partner coded flights, but also if they are like AA then there could be a hard cap on max miles earned on a revenue based ticket, we'll have to see. From just a pure mileage earning perspective AS Mileage Plan is pretty darn sexy for that trip, however you won't earn any status without a pretty substantial number of AS metal flights. AA also has a pretty good award chart for some regions and credits quite well for BA / IB / AY / QR flights, but pretty miserable for AA coded flights themselves, if you credited to AA you'd want to absolutely minimize any AA coded flights... the good news is that a lot of them can be booked as codeshares as long as AA isn't the ticketing carrier. (Travel agent still can, but word is that AA will insist on using their own codes if booking with them directly).

If you're just after status then you might still credit to BA, but you'll want to do some comparisons between BA, IB, and QR as they all earn Avios, all can be transferred between the programs (and EI) and all will get you the same lounge benefit. All 3 are similar but slightly different in how they award status points, so you really have to put it down to the actual itinerary you settle in on. Apparently IB and BA status point earning won't change in the new revenue based program. If you go with QR Privilege Club you'll probably earn 125% of miles flown on most the flights and a bit better (175% or more depending on status level at the time) on QR flights themselves.. That's not bad but also not the greatest you can do. QR also has reduced elite point thresholds for renewals to make it easier to keep once you earn it.