Honestly at this point, an ACF for the RNZAF/NZDF is more a Want by some, rather than a Need. I do feel obligated to point out that military & naval capabilities are very often like handguns, in that one does not need them, until they need them badly. And by then, it is almost always too late to get them...
For those that are tired of hearing my bang on about this, feel free to pull me up short. What I feel NZ needs to do is sit down and take an honest, rational and non-idealogically driven look at NZ's total defence situation in both the near term, as well as the likely situation into the 2040's. A plan to 2035 is nice, but that is only slightly longer than many initial procurement cycles, being only ~17 years away.
When I speak of the 'total defence situation' I mean more than what most people, even many here on DT, consider relevant to NZ's interests. One of course must consider the situation within NZ proper, and the home waters and airspace. NZ's EEZ and the EEZ's and SAR regions NZ has responsibility for is another obvious area to consider. What seems (still) to be an area people overlook is the SLOC over which kiwi goods transit to get to foreign markets and just as important, foreign goods transit to get to NZ. Expanding out even further is the security situations for both the various foreign markets for kiwi goods, and the sources for goods/materials NZ imports. Threats and hazards to the SLOC can impact NZ's trade by increasing the cost, the transit time, or the availability of goods. Unsafe conditions at foreign markets and sources can outright close export markets for Kiwi goods, as well as deny NZ access to materials and goods.
The current situation with N Korea is a very good example. If that erupts into a hot conflict, especially if there is significant damage and/or the use of WMD's, that will disrupt the SLOC to several trading partners, namely China, Japan, and S Korean. Depending on just how bad things get, it could also mean the actual destruction of various markets and sources which have active roles in the Kiwi economy and international trade.
NZ needs to have a defence force capable of independent operations to protect NZ and NZ interests, which is also able to make useful contributions multi-national coalitions and be able to operate with allied forces. From my perspective, that also means having more forces able to operate in Chapt. VII-level responses than the Chapt. VI-level deployments which past gov't seemed to believe (naively hoped?) was going to be the norm. NZ is too dependent on international trade to realistically be able to avoid being impacted by events elsewhere. An area where I fear the impact of those who wear rose-tinted lenses is in NZ's ability to have a say in outcomes without providing real, measurable and significant contributions to achieving said outcomes and/or suffering significant/unnecessary losses due to a lack of sufficient forces which are properly trained, kitted out and sustained.
The small size of the NZDF, and the tiny budget will of course make this difficult, but decision makers need to realize that security conditions are not all milk & honey now, while there is a chance to make changes which can have an impact.