Taiho versus additional light carriers

Should Japan have built more small light carriers instead of Taiho?

Probably not: a slip could build only one hull at a time, and abandoning Taiho was unlikely to produce enough completed light carriers to outweigh losing a full fleet carrier.

The choice turns on slipway capacity rather than a simple tonnage exchange. One large hull occupied one slip, and replacing Taiho would not have yielded several completed light carriers in the same time; perhaps one additional light carrier and part of another was more realistic. Given that constraint, completing a full fleet carrier made better use of the available building position.