high altitude balloons with a few air to air missiles slung underneath is another option
some balloons will be armed , others won’t
an aerial minefield will mean incoming aircraft won’t be able to know which balloons are harmless and which aren’t
you might have circling drones with very long wings for lift powered by solar
the drones circle around endlessly dropping air to air missiles as the enemy approaches
sure you might be pop off a few missiles but counter measures can be dropped by hundreds of these things filling the sky with chaff
friendly aircraft will fly into the minefield being covered by the drones above and around
australia would be better off fighting a defensive war assuming a looming battle for foreign owned assets in say 30 years time
an australian government comes to power that promises to nationalise foreign owned assets , the foreign power with most to lose objects and decides to seize back the nationalised assets
australia then fights a war to stop aerial bombardment
ICBMs strike the major capitals with conventional warheads MOAB or FOAB style , in a war of assets the cities are of no consequence, the assets are in the agricultural/ mining output, most likely mining sites would be seized back after a first strike crippling the cities causing law and order to break down after three days of power losses and no running water
a counter strike by australian ICBMs hits foreign assets as a tit for tat blow
australia readies its armed forces (a sizeable number of casualties were taken in the first strike on military bases)
foreign subs land troops on to the mainland to disrupt railway lines/ road networks , collapsing a bridge across a motorway chokes traffic, planting timed explosives in the rubble keep clearance crews away