Slipways and the infrastructure shortfall

Did infrastructure limit Japanese cruiser design mainly by size, or by the number of ships that could be built?

Both mattered, but additional medium-sized yards, slipways, factories, and standardised production could have increased output far more than another giant dock alone.

The relevant infrastructure extended beyond the giant dock needed for a Yamato-class battleship. Two cruiser-sized docks could occupy roughly the width required by one much larger capital-ship facility, and suitable bays also allowed docks to be built outward instead of excavated inland. Smaller slipways, fitting-out facilities, steel works, and armaments factories could therefore have expanded output significantly. Japan could justify such construction as merchant-fleet development or as infrastructure appropriate to its treaty status. Greater Army-Navy standardisation of guns would have increased factory efficiency still further. These reforms would not make victory over the United States likely, but a better organised war economy could inflict more damage and prolong the conflict.