Before they become a permanent resident? I don't think that is a limitation...
A friend of mine from Perth is a JET teacher in Kobe and he ritualisticly has been exporting one car a year for the last 4 years to AU. He owns them for a year then imports them into AU as Personal imports. They don't need compliancing per se other than the basic roadworthy stuff and it can be any car and any year at all (modified or one already sold in AU).
But, you have to prove that you owned the car for a year over their with insurance, parking space, rego papers etc. Thats more difficult than it sounds as it's all extra paperwork to keep track of. Can't remember exactly which taxes you are exempt from with personal importing, but I'm sure someone else can post about that.
It's definately worthwhile to do if you want say a V35 Skyline 350GT or a recent model like that. Even thought they can be complied in AU, you'd be saving $$$$ by doing it personal import. On the other hand if you wanted a car that can't be complied in AU for whatever reason (eg: Evo 9) it would be worthwile doing aswell. The only downside(?) is that you have to sacrifice a year of your life in Japan...