Nothing sarcastic, can make an exciting single-player campaign of the USSR against Japan. There is everything to play in the spirit of the Company of Heroes:
stealth mission
paratroopers behind enemy lines
Marines assault Islands
Breakthrough fortifications.
And about the Japanese in multepleer:
from multepleer not take 100% of the historicity
You can go the way of Men of War: Assault Squad there is well established Japanese Army
Now try to balance the jap's paper tanks and their overall crap equipment against the soviets.
The Pacific Theater demands a whole different type of warfare. It is impossible to balance jap/sov and usmc/wehrmacht without creating a fantasy realm.