I find it amazing that a lot of Australians prefer Bali or Thailand, to visiting their own back yard. The West coast is an undiscovered secret, as as are the many beaches along the bight. A rail service would help open it up and possibly get people to move out of Sydney and Melbourne given the beachfront property in Queensland is already taken....
Australian's travel to South East Asian Countries because their dirt cheap to visit.
The West Coast Is a undiscovered secret, because of It's remoteness and harsh environment, people like It that way.
A rail service wouldn't be viable, due to no existent demand (TransWA don't even run road coach services up that way)
To lure people out of Sydney and Melbourne, they will still want a place that's within easy reach of these cities, so WA, NT not likely.
As for a Western Australian North West Coast railway, think about how the Queensland North Coast came about, the development of numerous railway (and tramway) systems along the Queensland coast (that linked the Inland hinterland to a sea/river port for coastal shipping) they progressively all joined up (apart from the Cooktown system) In an era where there were no all weather sealed roads and no commercial aeroplane services.