if we did capture Kaga, we would be able to get a much more detailed look at the ships designs, and how they operated them, as i am sure that are many pages of "SECRET" and "TOP SECRET" that can help the Allies in fighting and understanding the other ships in the Japanese fleet. as well as potentially a few Zero's to learn how to work and their capabilites. Then, propaganda, keep it in Pearl or even send it to California to keep it safe, and propaganda reasons. THen, after the War, use her for Atomic Testing.