Let's go back to the original scope of SEA 1180 in the 2009 DWP, it was to procure a class of 20 'identical' ships to replace 26 ships of four separate classes. The only differences would be by using various mission modules to achieve the task required of this class of ships.
The basic spec for these ships was to be 'up to' 2000t and to potentially have the ability to embark a helicopter or UAV's. A ship of similar capability to match that spec would be for example (but not limited to), the Damen OPV 1800, which is 83m and 1890t (according to the spec sheet) and has an aviation capability too.
Roll forward four years to the 2013 DWP, the Gillard Government put SEA 1180, as proposed in the 2009 DWP on the back burner. The plan was to replace the 14 ACPB's with another class of PB's (sooner rather than later), possible candidate could have been a version of the Cape Class PB's for example. The MCM and Hydrographic ships would have their lives extended until a longer term solution could be delivered.
Roll forward a bit further to now, the 2016 DWP, and we have a situation somewhere in between (say 2/3rds) the way of the original plan, 12 OPV's to replace the 14 ACPB's, (pretty good result in my opinion), the MCM's will be upgraded to operate until the 2030's (and who knows, the various 'remote' systems of the future may mean that some additional OPV's could end up being ordered too, the Government keeps talking about 'continuous' shipbuilding, etc). And lastly the Hydrographic fleet, the DWP says that a 'mixed' solution of Military and Commercial capabilities (whatever that means?) will replace the Hydro fleet, and they talk about 'modular' systems, could also point to some RAN ship having that modular system, (more of the same OPV's?), who knows?
Anyway, so much for the history of where we've been and where we are now over the last three DWP's.
So back to the here and now, I still don't understand why you would want to change a single class of 12 ships into 12 ships of three different classes?
Having a mixed fleet of 12 ships (to replace one class) is going in the complete opposite direction of the original SEA 1180 of having one class of 20 to replace four classes of 26 ships.
You said: "given how similar (or identical) the systems would be between 1800 - 2400/2600 the transition or progression of sailors across the vessels and associated training burden - is not out of reach"
But having had a look at the specs of the 1800, 2400 and 2600, shows that they have different main engines and auxiliary power generation equipment for example, and that's only the very very thin edge of the wedge.
Instead of '12 of everything' we would now be talking 'nine of this, two of another, and one of another', what is the cost of all of that??
If the Government is saying that currently we are going to have a class of 12 identical OPV's operating at one end of the spectrum and at the other end of the spectrum, the big guns (the AWD's and Frigates), well I'm satisfied with that to have that distinction between their various roles.
But if sometime in the future, say in the next five years, we end up with an update of the DWP or IIP (as may well happen), then if there is a need for a capability that sits somewhere in the middle, then maybe then it's time to look at a new or different class of ships to fill that potential void.
It might be called a Patrol Frigate or a Littoral Combat Ship (and not suggesting any designs if such a requirement was to appear), let's address it then and there.
At the very least it might be worth recovering and storing the various weapons and sensors from the FFG's and eventually Anzac's for potential future use (that's if the cost of recovering, storing and eventually refurbishing that equipment was worth the effort).
As you said, nothing is set in concrete, all true, but I don't think we have to start inventing new OPV roles above and beyond what is currently planned.
Cheers,
