So, this six submarines, are more of training submarines than real- operational ships. And you can see that, with exception of this 12 minesweepers, China didn't get any new ship from 1947 to 1950- just because, they simply have no trained crews for them. Or, indeed, a compelling need for a strong navy either.
Okay... in that case my recommendation is for the ROCN to have three submarines rather than six, which would be easier from a crewing perspective. A good case in point is that the JMSDF from memory used a former Gato class submarine as a training platform prior to re establishing the submarine arm.