"The Soviet Union has a new unique tech-tree. There are three unit production buildings: The Red Army Infantry Mustering Tent, the Soviet Support Barracks and the Russian Tank Hall. You can build any one of these buildings at any time, given the resources. Each building has three tiers. If you only have one factory building, you can only build units of the first tier. As soon as you have any two different factory buildings, you unlock tier two in both of those buildings. With all three buildings, you can access all tier three units in all three buildings."
This is directly from the guide. It would explain everything to do with the issues in balance and why the soviets have such a good early game.
If this was implemented then the Soviet union would have to go through 130 fuel before they could even purchase an is2 and the red army would have to decide whether to get either support weapons or to wait for medium armor instead of going straight for panther killers.
IMO this would solve the balance issues of Russians in mid game.