Yes, I think Japan would have to give up build slots for aus from late 2029-2033. 3 of the 9 expected in that timeframe. Would add a couple years to the Japanese timeline and they would have to order additional equipment but not 5+ years in advance.
FFM is much bigger, 1,000+ton heavier 142mx17m and taller compared to the Mogamis 133mx16m. I doubt the drumbeat can be sped up.
12 new FFM in just 9 years is fast, 15 seems very unlikely.
Hi Reptilia, I have a similar view on build time, but different take on Japan's ability to expand production.
I can't find a lot on the Japanese ship building cadence, however they have been able to consistently pump out two Mogami vessels per year to date from the two shipyards (Mitsubishi and Mitsui). Mogami production (the original 12) is due to finish in 2027, with the first completed back in 2022 and first of class steel made in 2019. From first steel cuts to launching takes about 12 months, with an additional 12 months to commissioning. So a six month cadence, a two year build and an eight year program for 12 ships. That's pretty good.
The first of their new FFMs is from what I have read due to be laid down in 2025 and for commissioning in 2027. They have not provided a launching or commissioning schedule from what I can find, but I can't see a reason for them not to maintain a similar production rate on the new FFMs. So they should complete the 12 new FFMs sometime in 2033/34.
I get that the new FFMs are bigger than the Mogamis, however much of that is simply stretch for larger weapons holdings and sensors. The baseline systems (propulsion, auxiliaries, navigation and possibly the combat system) would remain very similar, with some minor to moderate updates. The hull form has not been significanly modified (bit longer, bit fatter, but much the same shape). While there is some additional design time (hence a pause in production), I would be of the view the changes would not significantly extend the build time. Overall, I don't see them as much more than a second flight of Mogamis.
Of note, if weapons are a holdup on the schedule, we could always take a leaf out of Japan's book and receive them say without VLS and fit it later. Or as earlier suggested we could use some of the ANZAC fittings. The gun would be ideal to transfer for instance and I think it has been kept up to date with the modern standard.
As Reptilia states, the new FFM build program overlaps the required time for the first three Australian GPFs. There are two options, Japan gives us slots in their program and accepts a delay, or Mitsubishi increases their tempo. My view is that Mitsubishi could increase their tempo though expanded use of the Mitsui yard (which they purchased a few years back), so capacity on the steel side. There might be some issues with long lead parts, but engines should be available in the timeframe, combat system and radars remains to be seen.
The Austrakian government has been telegraphing the GPF schedule for ages, so I would view that Japan and Mitsubishi have an answer for it.