Why not take a SYD-AKL-SYD sector when you visit SYD? You have enough sectors available but will have to slum it in Business as no OW seats in First trans Tasman.
(edited: I now see you have several sectors in some of your 12 lines shown above and have actually run out of sectors if you ticket as shown. Maybe you can visit NZ next time or do a separate non AONEx trip ex SYD? )
I haven't planned out my travel in Oceania, but I am certainly going to purchase some separate tickets and will make it over to New Zealand, I just need to look at all of the options, including the Visit Australia and New Zealand pass.