Ok im going to be the realist here and point out the flaw in everyones dreams
The reason we are looking to an Offshore patrol vessel larger then the ACPB is that the requirements have changed then what they were at in 2005 when we commissioned HMAS Armidale.
Right now our role is border security, and for those outside of Australia this now entails a larger role in Suspected Illegal Entry Vessels(SIEV). This can range from a boatload of 12 to 150 and beyond suspected illegal entry persons, and the ACPB is unable to bear the brunt of this mission. My first experience with this was 80 people, and we struggled to contain that many on our small platform with the small crew we have, since then ive had double that. While we have brought an adapt and overcome attitude, we have learnt the limitations of our boats.
The mission can now contain SAR, and if it does it brings an added danger, as some of my colleagues have found out with Siev 36.
Our ranges have been more then was planned, in 2005 it was planned to have a lone ACPB every few months sail to Christmas Island to conduct fisheries patrols. At this point in time, there is now a ACPB at all times at CI and can be supported by a second. The mileage this adds to the boats increases their strain and has lead to issues with the hulls as has been reported.
If we do go with an Armidale+ then we have gone cheap and inefficent. The OPV will need to be large enough to handle monsoonal sea states, and more sea days then what the ACPB was envisioned to conduct. The flight deck requirement is not for a seahawk with missiles, but SAR and medical evacuations primary, and holding large numbers of PII as secondary. Anything else is wishful dreaming.
We have no need for harpoons or any other type of missiles onboard a OPV, but a more advanced radar then what we currently have is a requirment. We need to be able to spot contacts at far greater ranges then we currently can.
The OPV will be a multi mission with packages for survey and mine sweeping, with mine clearence expected to be with a remote vehicle more then utilising the vessel at close range like Huons. This can be conducted if there is more room to store them, which is why we are planning a larger vessel.
We are not building a fleet like singapore with a small attack package, its not what we need! We need a larger vessel to be able to handle a larger role then we planned, and require. Lets get off the track of harpoons, and penquins and keep it more realistic.
As a side note to help clarify my understanding, i currently serve on Armidale Class Patrol Boats.
Have you looked at the Danish
Knud Rasmussen-class OPV? In full load displacement, it is comparable to what the OCV seems intended to be. My reservations on it stem from a lack of helicopter hangar (it does have a helipad & refueling capabilities), a listed range of 3,000 n miles, a max speed of ~17 kts, and accommodations for only ~40 people.
The design is apparently ice-strengthened, since the Danes commissioned the class for sovereignty, SAR and EEZ patroling in & around Greenland. They are fitted with two StanFlex container positioned, with room for two additional container slots. The sensor and electronics suite is also comprehensive enough to operate ESSEM via VLS, MU90 torpedoes, of 76 mm naval cannon. The 'stock' armament though is normally just a pair of 12.7 mm HMG's.
While I do not think the design would suit RAN needs 'as is', it certainly could be modified to make it more suitable. The principal areas which I think should be changed are the addition of a helicopter hangar, for if/when the OCV is deployed away from Oz/other RAN assets for extended periods. If/when a helicopter is not embarked, the crew could utilize the hangar space, or it could provide temporary accommodation to people from SIEV's. Additionally, room, space and weight should be set aside for additional embarked personnel, in case the OCV gets tasked with transporting and supporting a mission to a Pacific Island nation. The RAMSI mission comes to mind as example of this, where an ACPB was tasked with supporting land-based personnel. Having a supporting vessel capable of providing NGS if things go very pear-shaped, as well as having a helipad/embarked helicopter and likely better medical facilities would all be to the good. Again, if not used by additional embarked personnel, such facilities could be used as a temporary accommodations & holding area for people from SIEV's. The last thing which I think should be changed in a design for the RAN, would be the inclusion of a modular slot (or two) at the stern, for use in supporting MCM and survey missions, or operation of a towed sonar array.
While I would not expect the main fitout for the RAN would have all OCV's heavily armed with 76 mm cannon, ESSM, etc. Having the option for a few to be fitted out would be good, using a common module pool. The rest could remain with their normal fitouts for patrol, SAR, survey work, etc.
As for modules... I still think StanFlex would be the best way to go. The Danes have experience with their StanFlex modules from the Flyvefisken-class patrol boats, and have gone on to include StanFlex slots in three new classes of vessel, the
Iver Huitfeldt-class FFG, the
Absalon-class support/command ship, and the already mentioned
Knud Rasmussen-class OPV. Given that these classes are all new, with some vessels still under construction or in the process of being commissioned and entering service, I would expect that the Danes plan on using StanFlex or some sort of compatible follow-on module for the next couple of decades at least, so the module technology should remain relevant.
As for using LCS modules from the US... I would hesitate on planning for that. The US still seems to be having trouble with cost and effectiveness for the LCS modules. Plus the ease of swapping modules seems to have gone away significantly, with weeks required alongside now IIRC.
-Cheers