What if the Japanese decided that the Battleship was essentially redundant in modern warfare and instead decides to focus on constructing aircraft carriers instead? Basically, this would mean that from the 1930's on no further construction of Battleships occurs. How many carriers could be ready for the war and what effect would this have on the war in the Pacific?
Consider also that this would mean a much larger naval aviation program, which means that there is a likely chance that the quality of pilots could be replaced instead of a large drop off and corresponding increase in losses.