Basically like this:
http://www.coh2.org/topic/17208/omega-s-japanese-faction
Japan mass produced some decent medium armor, but never deployed it in combat. Allowing them to use those units (Which isn't that big of a leap considering this is a game where Russians fight along Americans) is all that's needed. Other then that the faction just needs lots of AT focused snares and abilities to make up for the lack of heavier armor.
