And sans overland, I think that looking again at a Ghan extension to MEL might be a useful examination given the previous time it ran it was the Overland that killed it due to competition (if i have my facts correctly aligned)...Your facts are not correctly aligned.
The Adelaide-Melbourne sector of the Ghan in the Serco-GSR days was just a normal Overland running in its normal path with a handful of cars from the Ghan attached for through passengers. They weren't competing, they were one and the same.
There was a wait of quite a few hours in Adelaide between the Ghan proper terminating and the Overland-Ghan departing, and the through passengers had to get off the train in that time while their cars were cut out of the Ghan consist and attached to the Overland.
I can't see Journey Beyond repeating it. It is their off-train experiences which have turned the muddled confusion of the AN/Serco trains (which never knew whether they were tourism packages or public transport, and did both badly) into a real tourism success story, and extending the journey to Melbourne would require them to drop one each way so the train can do the full return trip inside a week. They understand the tourism market too well to make the same mistakes the Serco-GSR did.
I wrote a lengthy reply to this, but Railpage swallowed it up.
Basically what is written above by JOP is totally incorrect. The Ghan ran as a totally separate through service and there is plenty of photographic evidence to back it up.
Agree....because fiddling with the route alters the provenance of the named train.
The Trans-Australian which originally began between Port Augusta and Kalgoorlie, for practical operational reasons had its route "extended" to Port Pirie in the East; then up to Perth in the West; and finally to Keswick Terminal in the East.
The Indian-Pacific being named thus because the service operates between Sydney on the Pacific Ocean, and Perth (originally Kewdale, later East Perth), on the Indian Ocean.
Originally, The Ghan began from Port Augusta...and later, practical operational reasons extended its route to Keswick Terminal.
Originally, if one travelled overnight from Melbourne to Adelaide on the The Overland; one transferred to SAR operated Adelaide to Port Augusta service; before finally boarding The Ghan.
A thought for Journey Beyond; for a helluva experience revive the "Tea and Sugar"...https://en.wikipedia.org/wiki/Tea_and_Sugar_Train
Remember crossing the Westbound "Tea and Sugar" at Tarcoola....where a bloke with a slab of coca-cola hitched a ride with us to Pimba...