The sticking point for the routing is really the Africa bit. If you were to convert the itinerary to an xONE4, something like:

lhr-ist-mad-cai-amm-bkk-bom-hkg-han-hkg-akl-syd-chc-syd-jfk-lax-lhr

then you could use the money saved to at least partially pay for a ticket from CAI or AMM to where you want to go in Africa. It is not possible to get to NAN on an xONEx fare since the QF codeshares that go there are on FJ metal. I guess you could replace ...SYD-JFK-LAX-LHR with ...SYD-HNL-LAX-LHR if Honolulu seems like a reasonable substitute for Nadi to you.