Luddi VII said:
This scenario looks good!

For the upgrade paths of the tanks, here is a suggestion. You don't need to use it.
The KV2 was obsolete by 1942/43. A better move would be to the 'Stalin' series tanks... JS1 or JS2.
I like the idea of having a choice to build either Panzers OR Panthers OR Tigers. Sliding scale shield costs etc...may complicate the game on your part, but the Panther was far better off-road than the Tiger and both tanks had their strengths/weaknesses. Most historians would argue the Panther was the better of the two and was actually put into service AFTER the Tiger. So I would adjust the upgrade path accordingly.
If you wanted to do the medium, heavy, heavier thing for Germany I would suggest PanzerIV > Tiger > TigerII. Either way, this looks like a phenominal job. I am a closet Civ addict and spend most of my time developing FPS custom maps and models for 'Call of Duty', so I appreciate the research and long hours put into making a mod. All this makes me a bit picky on historical accuracy though.
On the point of Divisions/Corps. Are you assuming Corps contain their own Arty support? You do a good job of penalty to movement for the bigger organiztions but at the same time, the corps would benefit from their own arty support organizations, especially the Russians.
Not sure that adding more and more special units like self-propelled arty is a good thing. They were support only and never in enough numbers to do damage as an individual fighting unit. Have you considered the development of ARMORED Divisions and Corps?? Where the inclusion of such heavy SP guns would be 'assumed'? That way the armor corps would have the higher attack numbers than a comperable stack of 3 armor divisions??? OR does that make it harder to say "Oh, is this an Armored Corps of PzIVs or Tigers?". Guess that makes trouble too. Ok... I just killed my argument for choices of armor to build...under that last theory you would do the upgrade route only for producing new units etc. But I do like the thoughts of building armored corps, expensive, but putting a LOT of hurt on the enemy.
Sorry for the ramblings. Hit a sweet spot of mine!