The price increases (10% per year since 2011) have created a market for stolen and counterfeit cigarettes already. Creating a slow-roll prohibition will not stop people wanting to smoke tobacco products - in fact, previous evidence (e.g. alcohol and cannabis as things most people know about) shows that people are motivated to partake by the very idea of it being illicit.

The product of US prohibition was the creation of extremely wealthy alcohol running families who are nowadays big (legitimate) businesses in North America, built up through the wealth of the illegal operations during prohibition.

While the intention (zero smoking) would save many from suffering horrible deaths, observation of basic human motivation suggests the NZ experiment is more likely to make a few people extremely wealthy and not actually stop tobacco smoking at all, no matter how much better off people would be by not smoking.