As background, we're limited to purchasing economy tickets for work and have to book them via a specific travel agent rather than directly through the airlines. On UA, their systems allow me to purchase the coach ticket via corporate, then call into reservations and buy up the fare. If it's done within 24 hours and you're buying up to a higher cabin (i.e. work paid for coach, I cover the extra $$$ to business), they'll waive all the change/hassle fees and reissue the ticket, charging only the difference in fare between whatever the original ticket was and the cost of the new one. Does NZ allow something like this? Given my experience with this sort of thing on various carriers, I'd believe anything from "of course they do this" to "are you insane, no way they do this!"

I'm coming back from AU next month and the SYD-AKL business fares are a very reasonable premium vs coach, so I wanted to get a small taste of the new NZ 789 premium cabin... ;-)