The GGL are great at sorting this sort of query out. If you can roughly indicate the flights you'd like to take, they will book you into the class below what you want using a joker, use the 241 to halve the avios cost, and then apply a GUF2 to raise you a class. Basically as a GGL you don't have to do too much thinking for yourself. It won't cost much more to go in F than J to be honest, just avios, and you have a ton of those and all the vouchers you need to maximise them.

Personally, with that haul of vouchers and certificates I'd fly myself to Sydney via Singapore in F on the A380 service, then on to NZ in J, but they can figure out routings.