I’m still doing the Russian wall, not sending them home. Personally. Just pull the units back one territory away from Japan, leave a single picket infantry there. Pulls the infantry away from the coast so you aren’t at risk of being bombarded to death, also should pull you out of aircraft range (but I doubt someone’s attacking that stack with just aircraft anyway). Still able to push forward and cause issues, invites Japan to make Mongolia yours (more infantry) etcetera.
Also, with the income increase, Russia should be able to send a few tanks over to assist. Seen some deadly Russian invasions into China early in the game! Really makes it a nightmare for Japan.
Keeping in mind, my idea of KJF is just making sure Japan doesn’t get big. Keeping them in China is very effective in neutralizing them, and with pressure off America in the Pacific (not completely off, but reduced?) then American can use those ungodly sums of money to pound Germany.
Again, the above are just my opinions, if you don’t agree that’s fine. What makes this game fun is that you don’t have to do it a certain way!