IMO, China will not attack Australia directly but it would likely support Indonesia to do so at a later date once Indonesia arms up and outguns us financed by the proceeds of its mineral's regime and the economic benefits of its BRI membership.
Indonesia has traditionally been our enemy and that resentment has been exacerbated by our invasion on East Timor and the consequent retaliation in the form of te Bali Bombings .
Indonesia has already outgunned us in GDP(PPP) as has China outgunned the USA in GDP (PPP) and we see how that has raised concern in Washington.
Let's face it, Indonesia has: - traditional fishing territorial claims to Northern Australia -have a huge population (over 15 times that of Aus) -a muslin country that regards Australians as infidels -have already got a substantial pro Muslim population in Aus.
Such a Aus/Indonesian conflict would not involve Nuclear Weapons and who knows what for of self-interest our US guardian may have in say 10 years' time given te recent Trump/Rupublicans' shennanigans?
IMO, our best long term strategy should be to: (a) nuclearise (b) pay for it by taking control of our natural resources and extracting optimum value (c) Like Israel, be militarily self sufficient to meet any local national security threat. (NB: Israel has not been subject to any serious military threat since it nuclearised with the exception of half a dozen Iraqui Scud Missiles during desert Storm)
Israel's last significant war war was in the mid 1970s, ten years before it fully nuclearised. Similarly , since Pakistan nuclearised, Indian agression has dropped down to occassional border skirmishes.
