That thing about worknig holiday visa is correct: I went in a farm for three months and I got it renewed for another year. In this way I am now working legally as a charter pilot and I hope to get sponsored from my company when my current visa expires (don't sweat: still one year to go). About instructing, it depends from the school: I know personally at least one case in which one overseas instructor was sponsored for a 457 visa. In other schools they will laugh if you talk about that, it just depends. Anyway at the moment here there's apparently huge shortage of instructors. If you got the visa, you won't have problems.
Ah, daria-ox: if you are "planning" to come here in 5 years, I would suggest you first to think about getting your "loads of experience"