What about more cooperation with Australia?
I’ve wondered if a cheaper option for the RNZAF would be to contribute to an extra squadron (or two) of F-35’s operated in cooperation with the RAAF. Flown as extra RAAF squadrons but the Australian government would allow NZ citizens to join the RAAF. The funding required from NZ would cover acquisition and on going costs of the aircraft. This way NZ wouldn’t have to recreate a fast jet training system and in house experience.
HOWEVER! This idea would have to be combined with a mutual defence treaty type of idea for two reasons;
1: to convince the NZ govt they would have access to the fighters in the event of a threat to them.
2: allow Aus to deploy the fighters to combat a threat to Aus eg the north, that also would threaten NZ (if Aus was defeated).
Important to note this sort of agreement would not allow things like the deployment to the Middle East of F/A-18’s without the specific approval of both governments.
Something like this could potentially be used for additional airlift capacity, naval amphibious ships or maritime patrol UAV’s as well.
Australia and NZ have a long history of cooperation in major conflicts and a regional threat to one country will affect the other. While there would be significant political challenges I think a level of cooperation or a combined pool of equipment could reduce some costs and provide a benefit for both sides.
There are bilateral instruments if carefully drafted in non mandatory language, i.e the use of 'should' rather than 'shall', that can give effect to mutual cooperation between nations that don't have to have the legal binding of the Vienna Convention on the Law of Treaties 1969 in International Law. It could be an adjunct 'Memorandum of Cooperation' to the current CDR agreement.
The best approach to solve the problem you suggested, and one which gives both sides independence, would be how things actually existed in terms of policy understanding between the two countries in the past. For example up to DWP97 spoke of New Zealand working with Australia to effect
strategic and operational weight, including the cooperation of acquiring mutual or complementary equipment to their mutual benefit. One can propound that the recent P-8A purchase by New Zealand is an example of the NZ Govt selecting a platform that adds to the cooperative strategic and operational weight of the ADF and NZDF, even though on a day to day basis the command and control of the P-8's rests with each countries respective Air Component Commander, as well as ongoing mutual cooperation continuing to exist in terms of training and supporting the platforms.
However, both countries can still exercise independent operational usage of their respective fleets to pursue their own national interests or policy goals. That said - that caveat is possibly in practice not entirely likely on the balance of probabilities to really create much dramas (The RAAF deploying some P-8's to Country X in the middle east and the RNZAF deciding not to is not a show stopper - in fact the strategic weight that New Zealand provides in that space can pick up the "local" slack one could argue anyway), and if an operational combat vignette under a UNSC CHP VII event was in order, it is likely that 5 Sqd RNZAF would come under the formal command remit of a RAAF led Air Task Force (Which if it is bigger and more complex than a Timor Leste event would be possibly subsumed itself under a US theatre level air command).
Because of the silo mentality that has built up over the last 20 years is not helping both nations in my view, a 'Memorandum of Cooperation' or series of MoC's that saw more emphasis from New Zealand in building back a greater degree of combat weight to both countries mutual security benefit would be a way forward - and to be honest is much needed. Back to the days of interdependence and back to the days of improved clarity. This Post CV19 world is a significant geo-political reset and both countries through necessity are going to have to move closer together (In fact are at present whereby PM's have been invited to virtually attend to respective cabinets ). So a MoC or further MoC's that could cover precise circumstances between the ADF and NZDF is very much needed.