if the ships you re shooting at are a couple of thousand km from the fighter bases why do you need fighter cover?
I just can't see a reasonable scenario where the RAAF will be fighting front line PLA (AF) fighters anywhere near Australia
If you believe that the Chinese are going to invade (say ) Brunei that is 2600 kms from Darwin - same as the RAF wanting to fight over Murmansk from Northolt = does not compute
Unless you SERIOUSLY believe that the TNI-AU will be a serious threat in the next 30 years the only reason to have state of the art fighter is to keep up with the USAF