If you do want, and are going to fly *A partners, (apart from SQ), you can go and join the Air New Zealand Airpoint Dollars rewards system.
I do realise others have joined the UA FF system in the *A liaison.
Yes, the points might be hard to redeem overall, but they do last 4 years, so even if you do fly irregularly with AirNZ, you still earn a few Airpoint dollars, and can use them at the end of the 4 years to reduce the AirNZ domestic fares, 20% of the domestic fares, can be paid for with/by Airpoint dollars.
I have recently joined them, and at the least, I do earn a bit.
I don't trust putting my SQ KF # into any AirNZ bookings anymore, my last one, MEL - CHC flying AirNZ with my SQ KF # in the booking got declined/rejected, and was in W class, which is an earn class liaison between AirNZ and SQ.
In the begining, I thought that being/flying within *A, would be a gain if I gave my SQ KF # into all *A bookings, ala the AN (Ansett) days, but seems that SQ is very picky about allowing points earn with partners.
Flying their own planes, with the SQ KF # in the booking, they issue points/miles very fast.
From now on, if I am going to fly a *A partner (non SQ), I am giving my Airpoint $ # instead of my SQ KF #.
If you look at MCT with the VA to AirNZ connecting to AirNZ dom flight, the MCT can be quite short, 1.5 hours, which might be ok, but I would prefer a 2 hour connection.
Or even overnight in AKL, or other city, and get the first AirNZ flight out the next morning, CHC - ZQN, AKL - ZQN etc, or ZQN - another minor NZ town with AirNZ link.
Ending the diatribe here.