This is something i've been thinking about.
Assuming that Japan still follows major political directions identical to OTL and that rest of the world is mimially affected.
How would you improve Japans chances of winning the war against the US, assuming you had 3 structural modifications, corrections or similar choices you could make. Say "favor carriers over battleships" "Use better aircrew training" "defend manchuko better" and so on.
How much longer could you give to the Japanese if they implement your choices exactly. And would you then say they could have won the war if they did them.
Major dates for declarations of wars should stay roughly the same, so no "stay out of war entirely" option.