Parcel post goes by road and Express by air generally.  One in twenty of our sales goes to W.A. I have no idea where they shop online, but my guess is, if you are going to wait 7 days from east coast you might as well buy from the Chinese drop-ship sellers who would use a consolidater into Perth with a 7-14 day shipping time.

There are many fulfillment businesses across the country and even Australia Post offers the service... at a cost.  Your idea is 20 years too late...