The 737-600 winglets pack isn't offered just yet, but will be real soon.
However - and this is where I got a tad carried away - the published break even distance/pax point is high, so Air NZ prob wouldn't bother with added cost/weight of winglets.
Fact is, it is the NG version of the current 733 - easy(ish) type rating upgrade - and can be flown with as few as 100 seats and still be a winner! Though it would be a heavy 100 seater, can see the expressions on the beanie counters now factoring pay rates!
Makes some sense. Doesn't it Pakeha Boy??
Which prob means it'll never be considered!