I think you have taken a fairly narrow view on this, I was suggesting pretty much refocusing NZ defence around it's strengths/needs. If we split these down into say:
- Disaster relief/support
- Helping out with coalition constabulary work (at sea & on land)
- Insertion and support of a SF unit and small SF support group.
It maximises the value of it's best assets by developing a compact/lite SF support group and moves away from infantry battlions.
You mentioned a Absalon/MRV, which is one option, but I was thinking more a cross between a frigate & RSN Endurance. A uniform class of 2-3 ships would actually improve availability (over 2 types). Would this be expensive....nothings free your right, but if a similar approach was taken as the RN has with the Type 23/26, with relevant systems being moved across, as the new ships come into service. NZ will already have a lot of they are likely to require.
I am not sure self escorting is such an issue and it depends of the likely threat. As an AA platfrom, a bigger ship will be better, and will certainly be more helicopter capable. Helicopters pretty much take care of small boats/FAC. I think access to a small dock will be a huge benefit in the future (and now) not only for logistics/assault but USV and ASW sensors etc.
The range and payload of a C130 is better than a V22, but then it's tied to a runway (even a rough one). Does NZ need the load carrying? Whereas the flexibility a V22 could offer, just an example instead of fitting SSM on a ship, you could fit NSM on a V22?
It not so much a narrow view, as it is a realistic one. How often has equipment (whether it is vehicles, aircraft, vessels, personal kit) been designed to perform several very different roles, and had the equipment be inexpensive, efficient, and effective? In my experience, few times, if ever.
Now, the sorts of characteristics of a good sealift vessel are quite a bit different from those of a good GP frigate. The sealift vessel would want/need plenty of lane metres for vehicles and/or aircraft, as well as displacement for the weight of cargo carried. Various fuel and parts supplies would be required, as would the appropriate work/machine shops and spaces, to maintain the vehicles for the embarked personnel.
There would also need to be plenty of space for the embarked personnel, both in terms of quarters, but also for PT, rest, med facilities, etc. In short, everything required to keep the embarked personnel ready and effective for when they get landed. Using the HMNZS Canterbury as a guide, a company group that NZ wished to have embarked and deployable along with their vehicles and four helicopters, would likely require a vessel in the 8,000 - 9,000 ton range. Possilby more if a welldock was included.
Now add in the sorts of equipment a GP frigate should really be equipped with, like air/surface search radars, illuminators, a combat data system, main gun (76mm/62 at minimum, a 127mm/62 would be better) CIWS, ASW torpedoes, non-VSHORAD SAM, SSM, naval helicopter and towed sonar array... Not only is that going to need space, the kit will also require weight. Where things could get awkward is that some things like the towed sonar array, would likely need to be co-located with the welldock. Making things even worse, the frigate kit would need to be able to function while the vessel was carrying embarked personnel and vehicles. That, or a second such vessel armed and operating in the frigate role would need to be available if/when the sealift role was being conducted within a threatened area.
If the RNZN only was able to get 2-3 such vessels in total, then the RNZN would not be able to rely on having two of the vessels available to cover the sealift and escort roles at the same time, not and have the RNZN meet training, maintenance and other deployment needs.
Now on to the V-22 idea. That idea is one that really needs to be killed, because it is not viable for the NZDF. In terms of personnel, the CV-22 can transport roughly the same number of personnel as the NH90 helicopters that the RNZAF is currently getting, and using auxiliary fuel tanks, has roughly the same range, ~800 km. This means that the CV-22 could replace the NH90 as a battlefield rotary airlift (which is what the V-22 was designed for...) but would be completely unsuitable as a replacement tactical airlifter for the C-130.
To really appreciate why NZ needs something like the C-130, or A400M, one needs to remember the distances involved. The two closest points between NZ and Oz are 1,491 km apart or slightly farther away than Rome is from London, and they are on Resolution Island and Tasman Island respectively, not on the mainland of either nation. The average distance between NZ and Oz is ~2,250 km, or slightly less than the distance between London and the Black Sea port of Odessa, Ukraine.
With these sorts of distances, and the potential need to airlift equipment and vehicles into or from areas which lack a cargo handling capability, then military airlifters like the C-130 and similar aircraft are required. This is from a range, payload, and loading/unloading perspective.
Smaller aircraft like the V-22, while suitable for replacing helicopters like the UH-1 or NH90, would quite literally fall short of meeting the range requirement.
Then there is the whole cost issue. The NZDF is essentially starved of funding, and there would not be funding for something as expensive as the V-22, which as I mentioned before, is more expensive per aircraft than a C-130J to purchase.
The V-22 provides a specialty capability which is useful to the USAF and USMC, in that it is a comparatively high speed, rotary medium lift. It is being brought into service to replace aging CH-46 Sea Knight. Both the USAF and USMC budgets are sufficient to provide some specialty capabilities. However, the NZDF budget does not have that sort of flexibility. Not to mention the sort of reconfiguration which would be required by other NZDF assets in order to accomodate a rotary aircraft as large as a V-22.
-Cheers