A heavily armed convoy escort depends on the war

Would a 9,000-ton convoy-escort cruiser carrying seventy-five four-inch guns and eight torpedo tubes have been useful?

Potentially in the First World War or for early anti-aircraft work. For the Second World War, it would be more useful as an anti-aircraft cruiser with larger general-purpose guns around 4.5 to 5 inches.

The proposed Ultimate Admiral: Dreadnoughts design carries seventy-five four-inch guns and eight torpedo tubes on about 9,000 tons. Its usefulness depends on the war in which it is meant to serve. Four-inch guns could be useful for First World War convoy work or early Second World War anti-aircraft duties. In a Second World War setting, it would look more like an anti-aircraft cruiser, preferably with larger general-purpose weapons around 4.5 or 5 inches. It would probably spend little time accompanying convoys unless it was particularly slow.