Could Ryujo work below 10,000 tons?

Could Japan have built the original Ryujo design under 10,000 tons?

Yes, if it accepted a roughly thirty-aircraft group and designed a true small carrier rather than forcing fleet-carrier capacity into the limit.

The Japanese design became problematic because it tried to extract fleet-carrier capability from a hull below 10,000 tons. A more modest cruiser-carrier concept with roughly thirty aircraft could fit the displacement much more credibly. HMS Hermes provides a comparison for how close a purpose-built small carrier could come to the same threshold.