One force-design improvement for each major World War II navy

What single technological or doctrinal change would most improve each major World War II navy?

Standardize British 4.5-inch weapons, build true Italian destroyers and German light cruisers, accelerate French Dunkerque derivatives, redirect Yamato resources, and properly develop or avoid Pearl Harbor as a forward base.

Each recommendation attacks a different institutional bottleneck rather than prescribing one universal ship type. Britain gains from standardizing on a dual-purpose 4.5-inch family, while Italy needs true destroyers and Germany needs useful light cruisers. France benefits from accelerating a capable Dunkerque derivative, Japan from redirecting Yamato-scale resources, and the United States from treating Pearl Harbor as a properly developed forward base. The common lesson is that logistics, infrastructure, production speed, and basing can matter more than a headline weapon or individual capital ship.