I know that there were efforts at making submarine cruisers prior to World War II, but this is about during and after.
During World War II, destroyers and converted transport ships were used as
radar picket ships. Submarines were later used to fill in the role at the start of the Cold War. These mostly consisted of World War II vintage submarines modified under the
Migraine programs, but two
Sailfish class conventionally powered radar picket submarines were built, as well as the nuclear powered
USS Triton (SSRN-586). While
Triton was planned to be the first of a fleet of nuclear powered radar picket submarines, aircraft proved capable of taking over the fleet air patrol role. Also, the program probably fell victim to the same budget cuts that curtailed procurement of the nuclear powered
Enterprise class aircraft carrier and
Long Beach class cruiser.
Submarines have taken over a variety of roles, especially with the adoption of nuclear power, and the surface to air missile was becoming a mature weapon by the late 1950s. What if the two technologies were merged? Also, the role of the radar picket seems akin to a World War II/Cold War re-imagining of the scout cruiser. Since naval warfare in the late 1950s was starting to move towards missiles, could submarines have further taken over roles typically meant for cruisers, including the surface warfare role, or at least evolved into it over time?