The risk NZ would run if we tried to do that is it would probably be the end of the frigates for Navy. It may well be deliberate keeping the OPVs at a lower-end of the spectrum. Having said that, the replacement should be larger. The flight deck on Protector is marginal at best, and something being able to take a NH90 would mean far less compromise in naval aviation (and with a corresponding increase in ability to support other tasks).
If people in NZ truly see OPV's armed with a 25 mm gun fore and aft, and able to support an armed naval helicopter as an appropriate replacement for a frigate, I have to assume they either (a) smoke funny cigarettes, (b) regularly consume enchanted fungus, (c) have very thick eyewear, tinted a specific shade of red, (d) regularly take various pills with psychotropic properties, or lastly (e) have completely forgotten or are otherwise ignorant that they live on an island-nation dependent on maritime trade, and that their nation's trade lanes pass through a number of areas with active claims disputes, and other areas which have seen active combat in living memory.
I have a comment which will appear below about NH90 ops.
It's positively magnificent compared to Canterbury
For this, I refer back to my comment a posts ago about skinflints, fools, or deliberately trying to render the NZDF impotent as a combat force. One needs to remember that HMNZS Canterbury is (or was supposed to be...) a multi-role vessel (MRV). Amongst the intended roles was a patrol capability, ignoring the issue of different characteristics making vessels good at sealift vs. good at patrolling...
I was under the impression it was part of the remediation program, perhaps in receive-only mode? There was a whole-of-govt satellite AIS contract put out for tender maybe 16 months ago. From memory part of that brief was for OPVs being a recipient of the information, via NMCC.
While SATCOM might be nice to have aboard an OPV, particularly when far from other assets, I had more in mind a Link 11 or perhaps Link 16 capability. Something where a contact detected by another NZDF asset (P-3K, SH-2G(I), AW109, etc.) gets automatically relayed via datalink in place of the contact location and any details needing to be radioed over.
AN E/O camera should be achievable. Not sure about the radar though. It would be technically possible, but it would mean more weight. Just a decent FLIR would be adequate for SAR. The '109s have a winch fitted at the moment. It's a crap winch. Less user friendly IMHO than the Seasprite or Huey kit, and light years behind the '109.
Honestly, just an E/O camera might not be worth the expense for maritime search and resume. A sea search radar can scan a much larger area than an E/O camera can, in a given span of time. The E/O system is good for getting imagery and details, once the approximate location of a downed aircraft, disabled or illegal vessel has been determined.
Bang for buck I think upgrading a couple of NH90s and using them on the larger Navy platforms for utility roles would be more useful than '109s, but it would really come down to how the final numbers looked.
I do think upgrading all the NH-90's so that they can safely operate from HMNZS Canterbury in a wider range of sea states would be wise. Also if the Endeavour replacement does go through, and includes either a helipad, or helipad and hangar large enough for an NH90, then such an ability would make sense. There is little point in adapting the NH90's though, if the plan is to operate them from the
ANZAC-class frigates though. The hangars are realistically too small to support NH90's. If memory serves, when different contenders for the urgent replacement of the RAN's S-70B-2 Seahawks were being considered, the NFH90 was looked at, and it was determined that they would fit aboard the RAN FFH's, it would a tight fit. "Just enough room for a bee's d*ck," someone stated.