Why more Japanese carriers would not solve the air-group shortage

How much longer could Japan fight if every carrier it had built or planned appeared before Pearl Harbor?

Not proportionally longer, because Japan still lacks enough trained air groups and personnel to operate all of the additional carriers effectively.

Carrier strength depends on complete trained air groups as well as flight decks. Japan's existing difficulty generating enough pilots and other aviation personnel would remain after the extra hulls appeared. The same shortage applies to light carriers and larger ships. Without expanding that training and personnel system, the new ships would not yield a proportional increase in combat power.