Complex to manage, but the number of business class passengers that NZ carries via AKL to their network and their partners would warrant a cabin for them in the same way we see QF doing serving their hub.
Decades ago BA had a single domestic shuttle product (where everyone was fed and watered) but it didn't appeal to their US travellers. They introduced a business class cabin for the 40 minute hop to MAN which is always packed and extends for 9 rows usually.