The thing that I see is:
1. "The common defense of Southeast Asia;" – this hasn't been a thing since 1989. Most of SE Asia is happy to play with the Chinese. They don't trust America or China and they certainly don't trust America's self appointed "deputy sheriff" (how one Australian PM described Australia's role).
Indonesia and Malaysia both criticised nuclear subs because it also makes their defence forces every more vulberable.
2. "Stabilization operations in the Southwest Pacific;" – any area nearly totally ignored by Australia. The Chinese are making huge inroads here. At least the Kiwis understand this.
3. Missions:
1. "Anti-surface and ASW operations in Northeast Asia, i.e. around Taiwan and in the Yellow Sea;"
Neither of which are in Australia's direct interest
2. A "distant blockade" of China operating in "maritime chokepoints" like the Malacca or Lombok Straits;
Barring Chinese naval vessels and nuclear submarines from threatening Allied shipping in the Indian Ocean;
Really prompting an aggressive approach from China.
"3. Operations directly off the Chinese mainland to achieve operational objectives in Southeast Asia and the approaches to Australia."
Now they're getting cocky! Amazing to assume Australia can play an offensive game against a large super power. Literally it's like assuming Poland or the Netherlands could have smacked the Nazis in Berlin.
Oh and Australia lacks the one things that makes any of those missions plausible – nuclear deterrent
If China nuked Australia, USA does not have to respond. In fact I doubt the US would risk nuclear annihilation over Australia.
Finally any war between Australia and China and Australian society grinds down to the stone age – this is a largely deindustrialised society that doesn't produce virtually any key products.
Even oil refining is a dying industry in Australia – most of the oil refineries have been closed and there's only a couple left, one of which will close.
The country is in a far worse industrial state than it was in 1939 especially as modern life is far more reliant on these goods.
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The whole article presumes Australian subs can play some sort of offensive game that China does not counter
Furthermore like any western analysis it forgets the Chinese have their own subs, a substantial surface fleet an airforce, a nuclear deterrent as well as large quantities of sea mines and long range conventional missiles.