I‘m not sure how hypocrisy comes into it, but I think there has to be some realism injected. I think a lot of people are glossing over just how much would need to change for this to be a realistic possibility. I’m sure someone could develop some detailed numbers, but my rough estimate is that the NZDF budget would have to increase by around 50% over the next ten years to pay for the capital costs of acquiring all the capability (fighters, trainers, weapons, infrastructure etc), the costs of recruiting and training the people to fly and maintain them, and the costs of normal operations. That is a huge increase. Keep in mind that what is being advocated here is not a replacement of the capability the A4 provided, which, even when new, was at the bottom end of the fast jet capability spectrum. Nor is it a replacement for the capability the F16As would have provided, which was once again the bottom end of what would have constituted a viable capability. What is being advocated here is buying in the capability bracket of the F35, F15 and F18E/F. The RNZAF haven‘t operated a state of the art fast jet with that relative capability, and cost, since the meteor in the 50’s.
While I’m sure there have been some murmurings in government that the world is becoming a more dangerous place, it is a huge leap from there to increasing the defence budget by 50% to establish a capability that would only be useful in a very small number of contingencies. If NZ already had surfeit of capability options in other areas, and a fast jet squadron was a logical next step, that would be one thing. But there are so many other areas where the NZDF is deficient, and a relatively modest investment could make a big difference. If all the money is spent on fighters, though, those other capabilities will remain deficient, unless we go even further through the looking glass and imagine that NZ is going to double the defence budget or whatever.
To respond to your post directly, if NZ by some wizardry developed a fast jet squadron of course Australia would be grateful for the contribution. However, I’m not sure that is a good of measure of success for the tax payers of NZ when it comes to investing scarce dollars.