A Soviet carrier lease would demand an American rebuild

Could the Soviet Union lease its carriers to the United States for the early Pacific War and take them back later?

Only with difficulty. The US Navy would probably need a major rebuild of Soviet aircraft-handling arrangements before the ships were useful with American aircraft and procedures.

A temporary transfer of Soviet carriers could reinforce the United States while American carrier numbers were low. The ships would probably need a very large refit before entering US Navy service. Soviet aircraft-management arrangements might differ enough that American crews would want to dismantle and rebuild much of the carriers' operating spaces. The counterfactual therefore turns on integration time and conversion work, as well as the availability of a spare flight deck.