Japan's treaty choice would not solve its structure

How would Japan change if it kept the Second London Naval Treaty and built alternative capital ships and fast sloops?

The strategic result would probably change little, because Japanese building capacity limited simultaneous large projects even before wider strategic problems entered the picture.

Fast 2,000-ton sloops might be useful, and treaty choices could improve the pace at which some Japanese ships were completed. The larger constraint was a yard structure that could not readily build more than two or three capital ships at once. Yamato-scale construction consumed capacity that could not simultaneously serve a much broader fleet programme. Remaining in the Second London Naval Treaty might keep other powers inside the system longer and buy Japan time, but it would not remove the industrial or strategic limits. The route to war would change more than the eventual result.