Is it actually possible?
Who is the driver for such a decision?
Is this the best solution?
What is a realistic time table for entry into service?
Its possible IMO. Between the resources of Spain and Australia, that is nearly a dozen ship yards that could bit on block work and several yards that could be assembly points. But is it efficient? Does that meet the projects need beyond making it possible (local content, local industry, defence capability /oversight etc). The more complicated you make the project the greater the risk for costs, time, capability.
The biggest issues is this is all arse about. You don't get unsolicited proposals and then turn them into a project. Normally, even for unsolicited proposals, its for a project that already exists and is laid out. This is entirely unsolicited. It doesn't mean that the capability is perhaps not of interest, but it does make for a messy project with no clear pathway or target to aim for for implementation.
As things have arguably unravelled, cleaning up this mess is going to be a major effort.
If Boeing offers a C17 white tail or P8, then well a government could take up the offer and acquire it in a fairly straight forward way. The issues about ships like destroyers, is they are far more complicated than an aircraft and have larger crewing, industry support, development, etc.
Is it the best solution? Well is it an acceptable solution. The RAN had planning around a 4th AWD. There is arguably no time to go an select another parent design. Doing so would add 1-2 years easily, and push it into the 2030 and also a whole bunch of risk.
I was speaking to an RAN combat course instructor just this week who told me that the category he belonged to had a 20% exit rate in the junior ranks each year. Recruitment in the current economic climate is incredibly difficult, retention of junior ranks so you can grow them into Senior Sailors is key to expanding your workforce. How about you put forward your solutions to that first before expanding the current fleet by another 3 MFUs ?
Not sure how we intend to retain anyone if there are no ships and everyone stagnates at a desk. The current plan has the Hobart's coming out of the water and being 90% rebuilt in a costly and time consuming upgrade, with no alternative or replacement. Any DDG sailor will effectively have no role in the ADF during this 5-10 year period. In addition, the Collins are coming out too, and the Anzacs will need to undergo a smaller upgrade.
RAN might be a hardstand navy for the rest of the 2020's.
Ultimately, retiring Anzacs will happen and is the ultimate answer to crewing shortages. But for the medium term future of the next 10 years, due to platforms undergoing LOTE/Upgrades, it will be a shortage of platforms, not so much a shortage of crews.
Also there were four FFG's, and were meant to be replaced by four AWD's. In the end that didn't happen, Sydney, Darwin, Melbourne, Newcastle were replaced with Hobart, Brisbane and Sydney. No doubt the fourth ship would have been called Melbourne and the RAN wouldn't have retired a major fleet unit name with no replacement.
So the first additional Hobart flight II requires no more crew than we had back in 2015 and was in the original manpower budget of the RAN. The three Balikpapan class ships were also paid off in 2014 without replacement, so we are still talking about working up to the RAN of 2014 crewing levels with the 2nd flight II. While bodies and positions get re-assigned, its time to reassign back to active postings. That may be difficult, but it needs to happen, and it is where these positions need to be. If that requires a generation change to happen, so be it.
Growing the RAN is going to be a requirement going forward. We can't just grow the submariner force without growth in the surface force, most submariners start off in surface, prove themselves, learn basic skills etc. Injecting completely green sailors onto submarines is toxic for submarine crews and bad for retention. Our navy needs extensive LOTE/upgrades. You aren't going to grow the RAN with no ships during this period. Arguably no Anzacs will be decommissioned and instead they will receive another upgrade with NSM/ESSMII and some other improvements, but this means these ships also come out of the water.
Given where the hunters are to likely to be, our existing plan for the Anzacs retirement can be used to crew the new Hobarts. The original plan for Sea5000 was to cut steel 2019/2020 and the first ship to be delivered 2024.. Now we aren't cutting steel until at least 2024 with delivery, more like 2028-2029 realistically, perhaps even longer than that for first of class.
Maybe they can catch up later in 2030, but they are Frigates, not Destroyers. And realistically mid/late 2030's is when FOC of hunter capability will be realised. Possibly 5-10 years after the peak period of likely conflict.
While recruitment for the RAN is hard now, it is not going to get easier. Difficultly in recruitment isn't a reason to continue to underfund and underbuild the ADF. Unemployment is shrinking, there is a labour shortage. Our allies are facing the same problems or worse (Japan, Korea, UK, US)
But the likely hood of high intensity global conflict is now very high. Higher than during the Vietnam war. Highest since probably the Korean war or in the late 1930s.
Our scrap iron flotilla doesn't even have 5 destroyers currently...