Boredom leads to reading, reading leads to thinking and thinking leads to me boring the rest of you with an update to this thread. Most of what follows I have known for years but what I am trying to do is lay out the facts and where possible workout the thinking, therefore determine possible alternatives.
RAN post war destroyer plans were for two Group 3 Battle class destroyers an four AC Daring class destroyers. Two of the three war built Tribal class destroyers were to be converted into ASW destroyers while four of five transferred Q class destroyers were converted to Type 15 ASW frigates. Twelve Type 12 ASW frigates were planned but only four ordered, another pair, incorporating a number of Leander class features were ordered later as replacements for HMAS Voyager, a Daring class destroyer lost in a collision with the carrier HMAS Melbourne.
The fourth Daring, HMAS Waterhen, was broken up on the slips following cancellation in 1954, ironically to free up funding for the RAN to maintain a two carrier force, which, as I understand it, had already been done away with by that time. The intention had also been to retain either one or two of the surviving three cruisers as well as acquiring suitable new ships, this did not occur and even plans to use HMAS Hobart and possibly HMAS Australia as training ships did not occur. Also during the 1950s the RAN were concerned at the schedule slips on the Darings so attempted, unsuccessfully, to buy two Darings from the RN and even looked at acquiring US built ships. I am not sure what the planned fleet size was for the late 50s going into the 60s, but I do know in the late 60s the minimum required number of destroyers was set at 23.
The next major evolution for the RAN was the acquisition of guided missiles for air defence. Options including converting the Modified Leander class light cruiser HMAS Hobart into a missile ship, as well as a smaller, Tartar armed, steam powered version of the County class DLG and the USNs Bronstein class FFG were all considered while the UK offered a standard County, or even an Escort Cruiser design as alternatives. The selected option, once the preferred Tartar County was ruled out by the RN, was for two, then three US built Charles F Adams class DDGs, with consideration given to a fourth. Major modifications, including the incorporation of a flight deck and hanger for a Wessex helicopter, were considered but not proceeded with, the only major change being the replacement of ASROC with Ikara.
From what I have read it appears that the RAN, having had access to the test information on Sea Slug, as many trials had been conducted at Woomera in South Australia, was not at all impressed with the system. Other factors that may have had an impact on the preference for Tartar were, the RN had originally intended to acquire the system themselves, its compact size, compared to Sea Slug and Terrier, as it had been planned to convert not just the Daring class destroyers, but also the Battle class destroyers into DDGs. The conversion of these five ships would also have kept local yards busy for most of the 60s, which along with the cost factor usually brought up would explain the decision to build the ships off shore.
Now back to my subtlety different RAN, Waterhen is completed as planned while the RN transferred two AC Darings to the RAN in the late 50s. Two plus two CFA class DDGs would be ordered from the US, while Australian yards would convert the two Battle class and six Daring class destroyers into Tartar DDGs. The Battles would land all their torpedoes, Bofors and Squid for a single Mk-13 launcher two directors and a3D radar, while the Darings would also lose their after 4.5" and Limbos but gain Ikara in addition to Tartar. The cruiser HMAS Hobart may also have been converted into a CLG , possibly as an experimental conversion prior to the destroyer work.
Now with four new and eight converted DDGs, a CLG, four Type 12 and four Type 15 ASW frigates in addition to the two carriers, the RAN is in pretty good shape going into the 70s. They are only two hulls down on the required 23 destroyers / combatants but the CLG , Type 15s and Battles are at this point getting pretty old while the carriers are really too small to operate a sufficient number of modern aircraft. This should have been foreseen therefore a solution would have been to acquire Hermes when offered in 1965 for transfer in 1968, but then to have also requested Centaur but changed this to Victorious after her last commission was cancelled and two have requested two, or maybe all three tiger class cruisers giving the RN the cash they needed to build the first of the planned Escort cruisers.
The carriers would have operated the Trackers and Skyhawks ordered for Melbourne and Sydney plus Sea Vixens that came with the carriers and Tracers ordered with the Trackers. The Tigers would be converted into CLGs with the Tartar systems removed from Hobart and the Battles, while a new class of destroyers would be built to replace the Type 15s, Battles and older British built Darings. These new destroyers need not be DDGs but would have modern GT propulsion and helicopters, DDL or Tartar Shefield would be good but an evolved Amazon would do as there were so many missile ships in the fleet already, what I would really like is something like a Spruance. An enhanced version of whatever was built would then be developed to replace the Darings and Type 12s in the 80s and the CFAs in the 90s. Maybe instead of eight DD and twelve DDG,there could be ten of each. Also thinking either Melbourne or Sydney would be retained as a training / reserve carrier and the other converted into an LPH.
There would also be a full flotilla of ten Oberon class submarines acquired, with the last four built locally in the 80s before switching to a new design, based on the USN Barbel class, to progressively replace the Oberons in a continual build of five boats a decade.