Hey mate,
you have some really good suggestions up there.
The way I did it, and it might not be the 'best' way, but I managed to complete them all in 6 months and all passed was:
Get Human Factors, Met and Air Law done now. Give Performance and Loading a go, it is not difficult at all, and actually quite interesting.
Head over to QLD and see the great man himself, Nathan Higgins, and sit Flight Planning, have a week off to recover, then smash out Nav and Systems, and you're done. I think doing all 4 will explode your brain however, still certainly acheiveable.
Alternative to Performance and Loading is Systems. Maybe get that done before you head over east. Reason being, Systems is purely based on you reading the "questions and answers" and then doing the exam. I say that in inverted comma's because, really, it's up to you to read the text then go through and do the q's. Whatever you get wrong, study the question and the answer, re-read the section you got wrong, and I guarantee you will have adequate knowledge to answer the CASA questions. Nathan can't really teach you much on systems, it's all there, you just have to read and do the q's.
Up to you, however, they are going to suck, and you're going to be sick of the study by the time you're done, but once you start, go hard, dont stop till they are all done and best of luck!!!!!!!!!
Ray