I think you mean, F-35B, MAKO. MiGMasher, I think that's a little unfair. The Canberra Class are an excellent design and the RAN did do a comparative analysis of the designs available.
While the Makin Island is an improvement on the Wasp Class, it is still based on 20 year-old design and if I'm not mistaken the Spanish Navy intends to operate F-35Bs from theirs so the concept is there. Given that the ADF is of the unenviable position of defending 1/5th of the Earth's surface, Canberra Classes equipped with a squadron of F-35Bs would come in very handy and would go a long way in replacing the loss of air power projection with the retirement of the F-111.
Personally, I think it's an absolute tragedy that the RAN has been without a fixed-wing Fleet Air Arm and not replacing the Majestic Class Carriers and Skyhawks and Trackers was one of the biggest mistakes in the ADF's history.