But in that style of game you need other things because the allies can land in Russia and play the 'Vietcong army' and escape death by retreating across into Russia. Also, Germans need some other help and you'll have to give them Italy because they have all of Russia's might against them.
I thought I ruled that out?
Here's what I had attempted to say, in a different way of saying it.
1) Japan may not attack Red Territories or Russian Units.
2) Russia may not defend British or American territories. (Russian forces in British or American territories are ignored when combat with Japan occurs.)
3) Russia may not attack Japanese territories (defined as YELLOW territories) or Japanese forces. (Only way to liberate Sinkiang would be if Germany put a unit in there and Russia attacked the unit, thus liberating it (even with Japanese forces on it) for America. It would be immediately reconquered by Japan unless America put units there however.)) This discourages Germany from racing across the board to work with Japan on SBRing Russia as well, mind you.
4) Obviously, from point 3, Japanese forces in the same territory as German forces being attacked by Russia are ignored.
5) British and American units may only be in Red Territories IF they pay 1 IPC per unit stationed there. That's going to get VERY expensive if you attempt to build an army in Karelia or SFE or something. But it allows America to run away from China since that only costs America 2 IPC to escape (for the one round you are in Kazakh SSR) to save 6 IPC in units.