If Australia chooses a Japanese submarine this submarine is very likely to be fundamentally different from the Soryu Mark 2 (28SS) in several respects. Australia’s Japanese designed submarine:
1. should last for 30 years in-service including the diesels, hull, welds and Lithium-ion batteries (not just the Japanese standard of 20 years)
2. should be made of a hull and welds that can be cut and rewelded in Australia, by Australians
3. will be heavier to give it twice the range (12,000 nautical miles (nm)) rather than the current Soryu’s 6,000 nm
4. will be heavier to accommodate a vertical launch system (VLS) which may perform other duties (divers, LDUUVs) making it a vertical multi-purpose lock (VMPL)
5. is required by the US to have a US AN/BYG-1 Combat System which may (or may not be?) the new combat system fitted to Japan new Soryu Mark 2 (28SS).
6. it may be true to say the Australia's version of the AN/BYG-1 has almost the same access to the US run Seaweb network that US SSNs have (?).
7. unlike the Soryu Mark 2 Australia's sub will be fitted for and with Tomahawk cruise missiles and Mark 48 torpedos rather than Japanese Mark 89s
8. like the Soryu Mark 2 Australia's will not have Stirling AIP
9. this non-off-the-shelf submarine will therefore have specifically Australian only requirements. "Off-the-shelf" is more a political slogan, implying quick, uncomplicated and inexpensive. The reality is all countries want some modifications in major weapons systems and these systems (even "interim") usually take more than 8 years to be delivered.
10. it is likely to be much heavier, perhaps 3,600-4,000 tons (surfaced), than the 3,000 ton (surfaced) Soryu Mark 2
11. the heavier and Australian only features will make it much more expensive than the Soryu Mark 2 in terms of up-front price per vessel and this is not including all the very expensive backup-training-facilities costs (including translating 100,000s of owners manual pages into English).
12. Australia will require the transfer of more secret intellectual property details than the Japan’s military have transferred before
To keep his job and win the next Federal Election Prime Minister Abbott (most probably) cannot choose Japan until after that Federal Election which may be as late as November 2016.
If the choice of Japan is inevitable Japan can make the political risks of "Build in Japan" less by offering industrial offsets. The submarine builders, KHI and MHI, can offer much work for Australians in sectors unrelated to submarines. For example Kawasaki HI builds oil and gas rigs which could be built in Australia for the Australian market. Mitsubishi HI builds heavy machinery - much could be built in Australia for the Australian market.