|The RN operated a number of modernised carriers post war which were very expensive limited in number and had only limited service lives. One of the issues was that each modernisation was unique and as such could never provide the economy of scale that the USN acheived with their SCB 27 program.
The thinking behind the modernisation program was clear but the execution flawed. HMAS Illustrious, Fomidable and Victorious were ear marked for modernisation as a homoginous class to a single design. Indomitable was discounted as she was a unique derivative of the original design while Implacable and Indefatigable were less attractive than the original three ships as there were only two hulls vs three.
What I don't understand is why, when surveys showed both Illustrious and Formidable to be beyond economical repair from battle damage, the RN didn't substitute the Implacables. The Implacables were larger, faster, newer and in substantially better condition. In addition their, low height, double hanger design made them, both, unsuitable for operating postwar aircraft and easier to modernise, i.e. the two hangers could be converted into one without the need to raise the flight deck.
The other option that should have been considered was to forget the Armoured Fleets all together and modernise all four Centaurs to the same standard as Hermes, while relying on the Colossus and Majestic Light Fleets to fill in with Seahawks, Seavenoms and Gannets until the Centaurs were ready. They could then be converted to Commando Carriers inplace of Albion and Bulwark, as well as ASW Helo Carriers inplace of the Tiger conversions.