Just a though TH; you've got two flat-tops so they will both need some support from excorts, both aa and asw; even allowing for both not being at sea at the same time,
I had always seen the Rhodesia (Independence class) being basically discarded by the fleet once the Natal (Essex arrives). She is wheeled out for a cruise or two to support flying training when the Natal is not available and then in the early 60s converted to a LPH role. While still retaining the ability to launch and recover fixed wing aircraft she is mostly used to support a marine air-land battalion sized task force. Until replaced by purpose built LPDs in the late 1960s, early 1970s. A seminal event for the Marines and South African amphibious warfare being the intervention of 9 Marine Amphibious Commando (reinforced company sized) on-board the HMSAS Orange (Type 15 converted to APD) in stopping the Zanzibarian Revolution and subsequent genocide of the Zanzibari Arabs in 1964.
Just a though TH; you've got two flat-tops so they will both need some might need to consider increasing the value of your escorts, maybe going for Adam's class?
The 1955 fleet expansion program acquires six ex Fletchers with ASW modification (Weapon Alpha and ASW torpedos but still leaving three 5” guns) in addition to the three Type 15s. The three Loch class are still in commission but for reserve training based at Port Elizabeth, East London and Durban. They are still quite active units up until the mid 1960s providing a permament fleet presence in these eastern maritime cities as most of the fleet is based in the greater Cape Town area.
In addition three new build Mitscher class destroyer leaders are ordered from the US to provide AAW and ASW protection to the carriers. So that’s 12 quite effective (by 1950s standards) ASW platforms by 1960 and three more 1940s standard ASW ships.
Then in addition to all that there is the domestic shipbuilding program. As part of the quid pro pro of ordering three new build destroyers from the USA they agree to help establish a local destroyer production facility in Durban. The RSAN orders three Forrest Sherman type destroyers from this yard for delivery from 1960.
The Charles F. Adams is a natural to follow the Sherman class and the South Africans are very interested in the Tartar system. The plan in the late 1950s is to build Adams class to replace the Type 15s, Fletchers and so on and to refit the Mitscher class with Tartar. Also the Marines want a land mobile Tartar to replace the 3.7” HAA gun and Terrier to replace the beam homing Bloodhound Mk 1s they have. So South Africa orders a lot of Tartars and even establishes local production of the Mk 13 launcher (one of the reasons I have it on my later Zambezi destroyer) but events intrude.
While South Africa was ostracised by the US during the 1960s for Apartheid there is little motivation for similar in this timeline. Especially as South African segregation practices are en par with those in America and similarly in decline. However South Africa manages to get itself embroiled in a foreign war of a highly controversial nature.
In 1960 South Africa signs a mutual defence pact with Portugal to build a line of defence from Angola, across Northern Rhodesia to Mozambique. Also South African naval and marine power can be used to support Portugal’s other colonies like Guinea and those in Asia. Which results in South African involvement in the 1961 Goa War. Details are to follow but this action was called the “Three Day War” by the international press. The RSAN effectively destroys the Indian fleet (sinking the carrier Vikrant by airstrike and the cruiser Delhi by submarine) and hammers the Indian Air Force but is unable to forestall the surrender of Portugese India because of the land invasion of Goa.
The Western powers where generally very happy about the result of the Goa War. India showed her true colours at a time when they had been preaching Gandhism and peaceful neutrality on the international stage but suffered a humiliating defeat. America was more worried as this event was likely (and did) result in India becoming much closer to the Soviet Union. In an attempt to divert this shift in alignment they placed a ban on sales of major new defence equipment to South Africa. While spares and more discreet supplies would continue the USA would no longer sell any major defence equipment to South Africa. So the Tartar order was cancelled and South Africa turned to the UK for alternatives: being the Bloodhound Mk 2 for the marines and Sea Cat for the Navy and joint development of CF.299 (Project Cactus) later called Sea Dart to replace these systems in the 1970s.
Which means the Adams class can’t be built in South Africa. So another six Shermans to an improved design are built and then followed by the Sea Dart equipped Zambezi class.
I'm very interested in this AU, and so far it seems well thought-out; my only querie would be in some of the warships not being compatible, and maybe, due to age etc. not always effective in the roles assigned.
I have the Lochs being paid off in the 1960s and replaced by more torpedo boats in the reserve training role. The Type 15s are paid off from ASW role in 1960 as the first Sherman is commissioned. One Type 15 is then converted to a helicopter trials ship to compare Allouette IIIs to the DASH system, the later of which South Africa acquires. Another Type 15 is converted to APD and the third used as a spares hulk. Both remaining Type 15s are paid off in the late 1960s. The Fletchers receive FRAM upgrades in the 1960s with DASH but are replaced in the 1970s by the Zambezis.
The Natal is refitted and upgraded in the mid 1970s so misses Operation Savanah in Angola which causes great controversy. Because if it had been available it would have been able to blockade Luanda and stop the inflow of Cubans and Soviet gear.
The oldest ship is the Roberts monitor which replaced the Erebus as the long planned Cape Town guard ship. Though it is never used in this role. My idea here is to have the Abercrombie purchased in the late 1950s as a spares hulk for the Good Hope (ex Roberts) and then both of them rebuilt in the mid 1960s as amphibious landing support ships. Diesel engines and new upper works to give them another 20 odd years of life. Part of the amphibious expansion after the Zanzibar campaign. I’m not quite sure how but two ships each with two 15”, six 5” and four 3” guns with very low drafts and lots of armour are somehow going to help the border war. Terrorise the Dar as Salem, the Mozambique Channel and south west Angola or something.
The late 1970s RSAN would be:
# 1 Modified Essex class aircraft carrier
# 2 RSAN/French class LPDs (a mix of Ouragan and Jeanne de Arc designs)
# 2 Modified Roberts class LFS (with capacity to land 300 marines)
# 3+3 Zambezi class DDGs
# 6 Modified Sherman class DDs (with DASH and Sea Cat)
# 3 Sherman class DDs
Laid up in reserve will be the Mitscher and Fletcher class. The destroyer force will be contracting at this time because of a greater focus on strike craft for littoral warfare and a new carrier program.