There's a whole lot of wrong in this thread. Amazon isn't proposing to geoblock based on IP address and prevent Australians from even seeing the promised land (tm), they're proposing that if you select an Australian shipping address at checkout, you get redirected to amazon.com.au with the appropriate product added to cart (or the all-too-familiar "Sorry, this product does not ship to Australia. Please check other sellers that may ship internationally").
If you have a reshipper in the states, and select that as the destination address, Amazon will happily still ship anything in their catalog and not charge GST (as, obviously, they have no reason to believe GST is due). The reshipper may or may not then charge GST depending on the extension status of their middle finger in Canberra's direction.