Agree, I think we began to lose the design side with the DDL deferment in 1973 and subsequent cancellation (happy to be corrected). Hopefully the continuous build programme will result in the ability to design (or re-design) in country noting the Hunter and the Attacks will be build in batches and there should be evolution between designs.Up until the 80s, the RAN had its own ship design capabilities. They were got rid of following one or other of the reviews because they were “non core”. Now, if you want a warship design in Australia that is not a patrol boat or a fast cat you go to a design house for it - BAE, Damen, BMT, Gibbs and Cox, Navantia, Lurssen, Naval Group. They are all international companies and what you get will be a modification of one of their existing designs. You might get that modified, in fact quite heavily modified, in Australia but there is unfortunately no argument from their commercial perspective to set up an ab ignitio design capability in Australia at present. And certainly not if you pick each new ship you build from a different designer as that doesn’t generate a continuous workflow that can justify it. During the build process the design “migrates” to Australia for TLS purposes, but the design authority remains the original company from whom the Australian arm will need to seek deep level advice.
Bit of a pity about the DDL. It was killed by design creep and concern about the cost and technical (suspect you are across all of that). It would have been a capable ship compared to the FFG-7. It would have also kept the yard working following on from the DE build (mind you, the yard had a reputation for being inefficient and expensive).
I did have a plan of the DDL but appear to have mislaid it.