Extra tonnage only helps Ryujo if designers resist filling it

Would a higher treaty threshold make a modified Ryujo a successful aircraft carrier?

Yes, if the extra displacement is used to stabilize the original requirement. No, if designers immediately spend it on an even larger air group and recreate the top-weight problem.

Ryujo's historical difficulty was not simply that the treaty allowed too little displacement. A larger allowance could support a sounder hull and better stability. It could also tempt the navy to demand still more capability, consuming the margin and leaving the ship top-heavy again. The example captures a recurring procurement problem in which every new allowance attracts new requirements.