I assume you are talking about award travel since you post in a forum that its main goal is to gather miles and points for award travel.

AA has an Explorer award that is distance based instead of zone based.

There is an excellent STICKY in AA forum explaining the rules of this award because it is entirely different from the more well-known zone-based award among airline programs.

In that thread you would see lots of examples of creative routing. In fact one such recently involving Australia.

A 25K distance, 150K AA miles would be able to get you visit most of the places in the Pacific (without PPT or Easter Island) on you wish list in Business Class. 185K in First (if I remember it correctly). However, many flights on your envisioned plan DONT have First Class.

You can use BA Avios to do Intra-Australia, between Australia an NZ award on QF because BA and QF both belong to OneWorld.

UR points dont transfer to AA. MR points can go to DL or BA or CX though CX's Asiamiles are pretty much useless when it comes to redeeming award flights - high mileage cost + high fuel surcharge cash cost.

You would need to bridge some portions in the South Pacific, i.e. the French Polynesia with separate awards / pay tickets - because no one single award would be able to accomplish what you envision. You would also need separate award for the SCL side trip.

In the airlines you mentioned, basically they are across all 3 Alliances - so that would also imply that you may need/want to use more than one award as for example, you cannot mix QF and TG in one award - QF belongs to OneWorld while TG belongs to Star Alliance. Same holds true you cannot mix CX and SQ in same award - CX is OneWorld member while SQ is Star Alliance. FYI, award on SQ flights is notoriously hard to get in many routes.

I also note that you mix members from different alliances in one routing - it aint going to work. Award travel goes by SAME Alliance - i.e. you cannot mix JL with NZ - one belongs to OneWorld one belongs to Star Alliance. Air Tahiti Nui cannot be used as AA Explorer award as it is NOT OneWorld member but it is a partner of AA, so it can be used in a Zone-based traditional award.

You can also use one of the many award booking services to plan for your itinerary based on what your miles balances in each program. The fee is quite reasonable in my opinion, as they are the experts, know the rules of various programs, the route maps, the routes that easiest to find award seats, etc etc. Well worth the few hundreds you pay to get the chores completely taken care of by such service. My feeling is, for a total newbie, this type of services would be actually a life saver, especially for your desire of "I would like to have most flights to be n Business / First Class." and a very ambitious itinerary.