Regarding ship guns
A 4" is the smallest gun that can reliably fire a useful star shell - which is why we see it on most escorts and the ammo is light enough to be easily man handled
The Flower class corvette made sense as most Uboat's would be operating around the UK and in the Western approaches etc - it was only after the fall of France with Uboats now operating out of the French Atlantic coasts that U-boats had a clear route into the Atlantic
Before that the Flower was likely more than enough ship
With regards to small Cruisers - that was the job of the Tribal's in British service following the early 30s think tank on building 2000 - 4000 ton Crusiers with the other result being the Dido's et all
I don't have an issue with the 5.25 system - a lot of the critique seems to have started in the internet age and matches the system with late war radar directed us 5" systems with Proximity fused ammo verses small single engine dive bombers
The fact is that aircraft in the 30s were getting bigger, faster and flying higher and destroyers were getting bigger and firing torpedo's from further and further away
So the ability to lob a large fast Flak shell to a high altitude and a large fast HE shell out to the horizon on a DP mounting made a lot of sense in the late 30s and IMO continued too make sense.
Case in point - 1943+ German high level bombers dropping guided battleship killing bombs and the RAF dropping tall boys on Tirpitz
With an earlier unzipping of the treasury purse and with more of the modern Cruisers being made we can revisit one of my own Darlings
Yes lets convert the 4 Hawkins class Cruisers into 'Maritime protection Carriers' (I believe the below was by Peg Leg Pom?)
3 units converted in the early 30s - intended to provide 1 light carrier to a hunting group in the Indian Ocean, South Atlantic Ocean and Pacific Ocean with a 4th unit always in refit.
Operating 8 - 12 aircraft - mostly Shark or Swordfish with the capability to operate the Ampibs from the Cruisers and provide aircraft maintenance.
Can also operate as Aircraft transporters