What is wrong with the Anzac class frigates, I know they aren't that glamorous or anything but on paper they seem fairly decent in the low-end frigate role, upto 2 MK41 VLS, provision for 1+ CIWS, forward and towed sonar arrays, torpedo tubes, helicopter facilities, good range >10,000KM. Oldest one is about 20 years old, of course they will need replacing, and they should start thinking of that now, but OPVS armed with 50Cal machine guns seems like a downgrade to me...
And those AWD don't withstand the litmus test at all, they cost 1.5Bn each (there are cheaper alternatives for large VLS Air-Defence ships), will comprise the area-air-defence segment of the australian navy, using the rule of thirds gives us one ship on station at any point in time, and it is to defend approximately 10,000KM of coastline (ignoring the southern coastline). It is absolutely ridiculous, beyond absurd.
Lets be reasonable what Australia needs is large numbers of reasonably priced, affordable frigates in a high-low spectrum (similar to UK navy, or USA air-force), to defend the vast territories of australia, and it needs this before it talks about trying to build us cruiser style look-a-likes. I don't see what place OPVs have in a proper navy, when your typical lower-spectrum frigate i.e. TF-100, Meko-CSL or even a Absalon support ship, all suitable for an LCS role are already capable of peforming everything your OPV can and more. Additionally aerial platforms i.e. UAVs (zephyr or global hawk) are far more suited for the survailance role, and floatplanes/tiltrotors can perform rescue missions from very far away, and far faster than some slow OPV.