Industrial limits matter more than treaty limits

Would abandoning Washington Treaty limits have made Japan much more viable in 1939?

Not greatly: Japan's industrial capacity constrained fleet growth more than the treaty, and unrestricted building could still favour oversized capital ships.

Industrial and infrastructural capacity constrained Japan more than treaty ceilings. Ending the treaty restrictions would not create extra shipyards, skilled labour, machinery, or steel. On this reading, extra freedom would instead encourage resources to flow toward exceptionally large prestige battleships. That choice could leave Japan with fewer of the carriers, escorts, merchant ships, and supporting units needed for the proposed 1939 war. Legal permission to build did not guarantee the industrial ability to field a balanced fleet.