Try the following:
mel-syd-jfk-ord-lax-jfk-bgi-lgw,lhr-amm-fco-hel-fra-nrt-del-nrt-dps-nrt-mel-per-cbr-mel
Book MEL-SYD with an AA code, and SYD-JFK as AA7365 instead of QF107 and you'll achieve the AA Platinum challenge with SYD-JFK, thereby earning the 100% miles bonus from that flight (except the JL ones but you get nothing on CX in L anyway), and oneworld sapphire status after syd-jfk. You need to 'refresh' ur status with all the airlines so that your new sapphire status shows up.
You can take a little breather after returning to mel and use the rest of the SWP segments for a short weekend trip to WA.
Unfortunately some routes are non daily, such as amm-fco and nrt-mel so you might want to plan around those carefully.