As an ex-submariner I think there is a lot to be said for picking up the "o" names. These have history with two Oxley's and Otways's having been in service (these were the "O" class submarines purchased in the interwar years). There is a lot of tradition in this including the "Omerang" still carried on the Collins Class.Both already in use...
Oldsig.
HMAS Oxley (I) | Royal Australian Navy
So Oxley, Otway, Onslow, Ovens, Otama and Orion ................ pick another relevant O for the last two. I personly like two of the RN names in Onslaught and Opportune .... quite fitting for the current environment.