I'm reading a book about the sinking of Force Z, and the intro mentions the other choices available for a Far East Fleet base, including Hong Kong, Colombo and Sydney. WI, instead of Singapore, Darwin was chosen? Perhaps a deal could be struck with the Australian govt to build a railway to Darwin and develop the area to sweeten the deal. Such a choice could provide a more secure base which still has good access to the strategically significant region of South East Asia.
How would WW2 pan out if the fleet base was in Darwin? For starters the Australians would be keen to defend it and not be left to the mercies/circumstances of the British.