There is no such thing as EPA approval for ECU in Victoria. You cannot get approvals either realistically.
If the loom is too hacked up, but a new GTR loom from Nissan (~$600-700) and get a PowerFC ($900) or similar and go down that path.
At least then when you get defected, and it will happen, you can just put the stock ECU back in and away you go.
Whilst a new loom might sound expensive, if the F-Con is wired in like i think it is, it'll be easier and cheaper just to start over.
Also the fact ANYONE can then tune your car, rather than you be restricted to 1-2 people...