I need to push back on your analysis on this. Quite hard actually.
Indonesia lacks the force projection capability to even project an expeditionary force into Northern Australia.
Sustaining an expeditionary force into Northern Australia by Indonesia would leave it incredibly vulnerable to air and sea supply chain interdiction.
With first hand professional domain experience, and without arrogance or hubris, an Indonesian invasion of Northern Australia would be disastrous for Indonesia.
China invading Australia would entail a much more capable, but entirely untested, expeditionary force over much longer and far more vulnerable supply chains.
With just FVEY intelligence support and FVEY forces already forward deployed into Australia, the likelihood of China successfully establishing and sustaining a beachhead to break into Australia with a conventional invasion would be similar to that of Indonesia, due to very long and very vulnerable supply chains.
Unless China glassed Australia with nuclear weapons, any attempt by Xi and the CCP's PLAN/PLAAF/PLA to conventionally invade Australia would be a moon shot too far.
China's fleet steaming south would be severely attrited transitting limited maritime traffic route bottlenecks that would be akin to cattle chutes in a slaughter house, while China's own energy/food/raw industrial materials commercial maritime supply chains would be existentially vulnerable.
That's just to Australia's current fleet of Collins class submarines and tanker supported F35s.
Australia's AUKUS nuclear submarine investment will magnify that current independent threat to China's maritime supply chain.
Which is odd, considering this comedic skit is partially true:
https://www.youtube.com/watch?v=-cGYQneo-G8
Unconventional attack is far, far more likely. Thus requiring a focus on national resilience and adaptability to crisis.