Unsure of its accuracy but SPIRI reports the RNZN has had
"250(?)" CAMM missiles delivered. So stock numbers may not be a major issue as such (well currently, anyway).
IMO the next issue to be addressed, if practical eg weight wise, is to increase the loadout carried. Whilst the original "mushroom" configuration was considered to be "fit-for-purpose "at the time (over 10 years ago now), modern day events demonstrate that is no longer the case, even against ad-hoc adversaries, let alone against a well-prepared adversary (or its proxy gray fleet).
Plus also for geographical reasons i.e. the distance to be traveled from NZ to the AO (likely to be in the Indo-Pacific, joining a wider allied effort) and without needing to leave the AO and return to port to reload, be that NZ itself or an allied base if stocks could be pre-positioned there etc.
So perhaps options could include replacing the mushroom farm with a number of LM 3-Cell Extensible Launching Systems to fit within existing spaces (although unclear weight-wise as haven't seen any published figures for ExLS, and to compare it with the Mk41 VLS, which is also larger and presumably heavier. So making the assumption ExLS is lighter and more compact). If the ANZAC design originally had space reserved for 4x 4-cell Mk41, surely at least 4x 3-cell ExLS could be fitted, which if quad-packed means a 48 missile loadout. And if space/weight allowed additonal 3-cell ExLS then that's even better ...
So how practical is this? Well the mushroom silos were removed (and reinstalled) during the post-FSU upgrades here in NZ a couple of years ago for
Te Kaha to allow plant and machinery in the hull area to be accessed and replaced. So it seems this could also be done in-house, relativerly quickly. In terms of CMS integration, the ExLS is a LM product, LM make the CMS and are fitting this exact configuration to the Canadian River-class Destroyers i.e. design/integration are already in motion.
So for NZ IMO this would be an acceptable configuration for the interim until the ANZAC's can be replaced (or supplemented with in the early 2030's).
Sure 4x 4-cell Mk41 VLS would be a "better" system for numerous reasons but suggest it won't be practical, weight wise (it couldn't be done for NZ and Australia in recent upgrades), plus also the weight of Host ExLS needs to also be factored in, so instead address this (Mk41 or Mk41 + ExLS) in the ANZAC replacement vessel.
The second issue to be addressed, as Gracie1234 points out is the number of vessels for the ANZAC replacement. Three replacement ANZAC's would now have to be considered the "mimimum viable capability" (rather than two) but even that number would be questionable in these changing times, so numbers or configurations ought to be a little higher.
Whilst the type and numbers are under consideration as part of the DCP/fleet renewal, the Govt is also is also asking defence to look at "emergent new military technologies (such as remote systems), and how we can work more closely with partners" (
pdf page 86). So at this stage, there is much to consider what final fleet replacement options and configurations could look like ... but suggest NZ is looking closely at what paths its allies are taking, what could "plug-in" and what it can afford. I think it is safe to assume times are changing, for the better.