G'Day Jabawocky,
You are indeed correct. Keeping the F111s would have been an excellent idea to put it mildly. In deciding to retire them the Govt has effectively removed more than 50% of the RAAF s offensive strike capability.
See here for a huge amount of in depth info and analysis-
RAAF F-111
As many articles on the ausairpower website state and demonstrate through their in depth analysis and as was proven by airpower advocate Billy Mitchell in the 20s and 30s, the aeroplane was then and is now the dominant military platform in almost every strategic scenario and in many tactical ones as well.
Since WW 1 this has been proven in practice in countless battles.
Without air dominance/superiority any land or naval forces are simply targets for any well trained and equipped hostile air forces.
Whilst we certainly need well equipped and much larger naval forces to protect Australias vast sea lanes and maritime approaches, without a very well equipped and numerically strong RAAF to provide air control over those forces they are totally vulnerable to hostile anti shipping missile equipped maritime strike platforms like those proliferating at an alarming rate throughout the Asian and Indian sub continents.
Many of these types are vastly superior to our aging F/A-18As and even the soon to come F/A -18Fs.
The above site provides many hours of detailed explanations that are easy to understand by military professionals /analysts as well as enthusiasts alike on a multitude of topics including those I have mentioned.
Pity more politicians and media people dont get better informed on such matters.
Cheers