Firstly anything that Aus and NZ took from Germany would be handed back in the peace settlement, Britain would be desperate to get Germany off the Channel Coast and German New Guinea, Samoa etc would be given back.
This would make Aus and NZ very wary and pay more attention to their own defence, so the Singapore naval base agreement where Aus paid 20% and NZ 5% might not occur and RAN ships might not be counted in an analogue WNT or 1st LNT, or if Aus ratifies an analogue Statute of Westminster early it might pull out of any Naval/Arms agreements and build up the RAN and other 2 forces. This might not require Federation with NZ or Fiji, merely close cooperation.