In NSW if he gets his parents to buy and register it as a family owned car under their name [not his] then he can use it [or thats my understanding of it], but what parent would be so stupid.
And removing the turbo doesn't work cos the law goes off the model number of the car, and a Gtst is Gtst is a Gtst!!!
I would seek legal advice tbh, if he buys and smashes are you liable??? Is it the same as selling beer or cigarettes to minors??? I really don't know. There is a legal website where you can register and ask such questions for free, might give you a starting point?
I'll find it and post.
Here: https://www.lawanswers.com.au/categories/australian-legal-forums.21/