Nice work there. You've fixed a lot of annoying issues and balance problems for a variety of countries. Chears!
Alas, I disagree with your nerfs to USSR:
25% IC: 25% IC only balances out the -25% nerf the USSR gets so it doesn't produce too much IC and forces pre-war. It's not a buff. As it stands, human Germany outproduces +60% AI USSR. Part of this is that human Germany tends to push central planning, so USSR does not get a relative +25% IC. Another part is that in the opposite to what happened in history, human Germany’s production queue tends to be much more efficient than the USSR production queue (at best, it’s equally inefficient), both in not wasting IC on useless brigades and units, and in taking advantage of gearing bonus, which USSR AI neither has the time to, nor the ability to use. Finally, Germany gets a historical +20% Speer. In the context of the above, the +60% for USSR is necessary, and still too little to allow for historical relative production levels, even with production time reductions in the Manpower doctrine tree. That’s why there is a need for such a large unit spam.
Unit Spam: IMO, Ideally the unit spam should be reduced, say to a max of 700 divisions or so, and rebalanced to hit earlier, so that USSR has a good chance of surviving into 1942.
GPW Combat Buffs: I don’t like unit-level imbalances. However, I would prefer some form of frozen/blizzard buff to represent the fact that Soviet uniforms/arms/equipment were better able to handle the Russian winter than their German counterparts.
No, that 25 percent malus is wartime modifier. As Soviets didn't enter a large scale war like Germany until June 1941, It didn't have any effect except for short durations of Polish invasion and Winter War. Default value of wartime modifier is 1.0 and Soviets reach that 1.0 with 0.25 bonus. 0.6 bonus makes it 1.35. With that 60 percent bonus, Soviets have higher IC than USA which is extremely unrealistic in my opinion. BTW, they don't really need ICs for free units as they cost only 0.1 IC. That will affect "natural" divisions built by Soviet AI. When Germany is also AI controlled, Soviets are given that normal 25 bonus.
I think Soviet superiority is already there with higher reorganization rate. When you are bogged down in winter, they don't allow you to reorganize with continuous attacks.