But...it's how Relic translates this into gameplay...
Well now I'm on a new page so I might as well just quote it here.
Imo the British Commonwealth is the last powerhouse country in the war. Of late-war Germany, the USSR, the USA, and the Commonwealth, the latter is the only one not yet portrayed. These armies had solid infantry, solid tanks, solid weaponry. All other examples had either inferior infantry, inferior tanks, inferior weapons, or all of the above. Germany's allies relied on German equipment and/or were never far from German lines, while Japan used extensive fortifications, island-hopping tactics, and their powerful Navy and Air Forces.
Some examples can't even exercise their chief advantage in a game like CoH2. Take the Japan, how are you going to represent the IJA's extensive defense network that gave them the advantage they needed to even stay in the war? When America invaded a Japanese Island, traps were already set everywhere, mines laid everywhere, ambushers were everywhere, and tunnels allowed troops to move unseen and stay safe from months of artillery bombardment.
People might ask for Japan, but nobody says anything about how they will be competitive in 1v1 without also being overpowered in mixed 2v2. The only way would be to segregate the factions or take the ToW route and ban a very large array of powerful units that those factions possess, including medium tanks.