Devil's advocate, where is the competitive pressure to look after the higher end better? NZ has very little competition for a lot of it's routes. Sure TT there is some as in multiple destinations on both sides. Most other airlines offering competition are singular routes.

Are people going to move JQ domestically?

Unless NZ sees an actual risk and material difference with people voting with their feet.

People say they take their spend after gold or elite to another airline but NZ already has a lot of revenue from you at that point. There will be a % of elites who just don't change their habits gift or no gift (don't care, corporate policy, etc). So how much more would NZ have to spend per person with gifts to keep the elites who do move their spend elsewhere? Is the price of the gifts going to bring in enough profit from the elites who change habits? And covering the gifts for the people who don't change their habits, as for those people the gift is a cost with no benefit.