Interesting, so if you bring in an N-reg, which has to be owned by a US individual or a US company (probably registered in Delaware), and it stays on the N-reg then you may not have to pay Australian GST?
In this instance, I think it would be classed as a visiting aircraft, so no. It may (however) need to be re-exported annually.
We used to do this with Rally cars. The car would stay on German registration and once a year it would make a trip on a boat to NZ to get the customs entry. The car never left the boat, just went to NZ & back!
But, if memory serves me correctly, many of our airlines aircraft (Qantas / Virgin, etc) are owned by overseas based finance companies, but are registered in Australia with an Australian operator. CASA records CofA holders, not owners. They stopped recording owners some years ago. So, I think an overseas company could own a VH registered aircraft.
Treatment of GST for export sales is (incredibly) still covered only by a draft ruling. See here below. There is a specific section on aircraft.
GSTR 2001/D6 (Finalised) - Goods and services tax: Exports of goods (As at 29 August 2001)