One of the complaints of the secessionists’ was that the west was neglected by the Federal Government. I doubt you’d be able to squeeze much more in the way of defence out of Melbourne than the naval guns around Rottnest, Garden Island and Fremantle that the west could provide for itself.
This complaint you mention would be from the nineteen thirties in OTL (our timeline), not from the first decade of an ATL (alternate timeline) where WA doesn't join the Commonwealth at federation.
In this ATL there is the shock of the Russo-Japanese war and the end of RN bases in Australia to contend with.
I can't imagine that a Western Australia that was susceptible to Yellow Menace warscares in the late 1910s of this ATL would have the same complaints of the failed secessionists of OTL. Those WA politicians deriding the East's ability to safeguard the entire continent (and do so with the help of the empire, of course) would be at a severe disadvantage in promoting their own self-defence policy, as a Western Australian nation-state isn't likely to be able to raise it's own equivalent of the brand spanking new RAN.
Cook said:
Westralia would be wealthier than in OTL but not massively. With Forrest as Prime Minister of an independent Westralia he may have looked after C.Y. O’Conner and obtained loans from London for more Civil Engineering projects on a par with the massive Mundaring Weir and Goldfields pipeline projects.
This is pure speculation. Maybe it happens; more likely the failure of WA to join the Commonwealth has no effect on O'Connor's decision to blow his brains out, and he is thus unable to turn the desert into a flowering oasis.
By all means put this in a fictional scenario, as O'Connor's is a story worth knowing.
Cook said:
How Westralia’s Prime Minister Curtin manages relations with London, Canberra and Washington during World War Two could make for an interesting story.
I don't see why Curtin is bound to move to an independent WA after the Great War, as one of his motivations in OTL was that he was already involved in a nationwide Australian political organisation
and moving to Fremantle would not effect his participation in this organisation. Plus there is such a thing as butterflies in alternate history speculation. Anyway, like I maintain, Western Australia is unlikely to survive as a nation-state, not unless it came out of the 1890s so resolutely opposed to federation that defence and the maintenance of racist immigration policies were of little or no account in its political system (John Forrest was pro-federation in the referendum vote of 1900, after all.)