It is very hard not to get caught up in fantasy fleets and speculation, that's why it is important to wait for the various, nested reviews to come out.
The DSR is providing the high level strategic guidence, the high level AUKUS plan has been released, the review on the surface fleet is proceeding, I wouldn't be surprised if there is a more detailed review into the ADFs littoral pivot.
Selecting platforms, before this work is done is pointless.
Now for my gut feelings and fantasy fleet .
Australia's geography dictates cruisers, that is traditional cruising ships of war, as opposed to ships of the line / battleships / capital ships in task forces battle squadrons / battle fleets, built around major fleet units, or sea denial coastal forces centred around localised geographic areas.
The original cruisers were sail, sail and steam, wood, ironclad, or steel frigates, sloops and corvettes. They provided presence, trade protection, communications, transport, scouting, plus many other roles.
The ships of the line were the heavy hitters, they were a force in being to counter the enemies equivalent. Basically they worked on numbers, hulls, guns, combined weight of fire. Over the decades (centuries) they came to be supported by torpedo boats, torpedo boat destroyers, destroyer killers (light fleet cruisers), specialist scouts, fleet ASW, fleet air defence, and of course carriers.
Then you have the coastal forces, MTBs, sub chasers FACs, (larger ones being called corvettes or even light destroyers), even monitors and gun boats. Designed as short range heavily armed, hard hitting area denial capabilities.
The overlap was convoy warfare, where ASW required slow light ASW ships, and eventually carriers, as well as battleships on the other extreme to counter surface raiders (carriers with a small number of strike aircraft replaced these).
SSNs especially those with cruise/strike missiles are the spiritual replacement for heavy or battle cruisers in everything except trade protection and presence.
Our large, multirole destroyers and frigates are very much filling the larger cruising ship role, i.e. the traditional sail/steam frigate role, latter filled by the likes of the WWI Town class cruisers, or our WWII modified Leanders and Counties.
The inter war sloops and to a lesser degree the wartime River and Bay class frigates were the second tier, still multirole cruising sloops. It could be argued the the frigates where more improved corvettes than sloops, they were after all designed for the RN as replacement for their corvettes for convoy escort, while the Blackswan class sloops made up most of the ASW hunter killer groups.
The large Tribal, Battle and Daring class destroyers were very much designed to the interwar small cruiser, large fighting, or gun destroyer concept, often refered to by other navies as Destroyer Leaders (DL) and post war by the USN as Frigates (later cruisers).
The seaward defence vessels, the famous Bathurst class minesweepers/corvettes, were very much the lower end on the general purpose cruising ship of war. Not ideal, but what could be built in numbers at the time.
There were also transferred and legacy fleet destroyers, motor gun boats and motor launches but by far the majority were cruising ships, used in cruising ship roles.
Australia has never been big on fleets, task force's, battle groups, squadrons or flotillas as tactical formations. We will integrate with those of other nations but don't usually form our own. The RAN has traditionally, and remains a cruiser and sloop navy.
Looking through this filter the SSNs are battlecruisers, destroyers and frigates are the cruising frigates, ANZACs are the cruising sloops, and any smaller open water combatants are cruising corvettes.
