That's the trigger word, isn't it?.
But I understand. Lend Lease Bren Carriers weren't too common yet so I don't know. I personally think, if a Nation did not produce a class of vehicles that one of its opponents did... you should not try to "balance" it. Balance in video games is pretty much the same as having two teams with all the same strengths and weaknesses but with... different skins.
This isn't the case in war. Both sides had their unique advantages and disadvantages.
If you really wanted to go into it, I'd think that the only map where Soviet forces would NEED transports would be the tank level. You claim that SdKfz. 251's without a comparable Soviet vehicle would be, unfair? So be it. But give Russian forces a way to
get around this. Earthworks, ample amounts of terrain depressions and gullies, ruined villages and the like. Seeing as the tank map will most likely be in the fields West of the city, you would logically be having the Soviet forces defending.
Give them fortifications, give them cover, give them
what they had!
Touching on armored battles... I'd like to see future content packs that focused on certain areas. The thing with Ostfront was that it covered the whole war, but focused on almost nothing. If you look at DH you'll notice a superbly made set of Ardennes maps based around the advance of Kampfgruppe Peiper by SchutzeSepp. I understand a variety of maps should be in the first release, but future releases should see a detailed set of maps based on the area surrounding one of the original 10. There are so many great scenarios available to HoS mappers that aren't in the city proper.
I've gone off on a tangent. I'll just reiterate what I've said in other threads. Make
MAPS, not
LEVELS. 1:1 Maps and accurate loadouts based on Unit TO&Es will
balance themselves out.
Anyways, I'd also like to say that I'd rule out both the IS-2 and the Tiger I. The IS-2 for the obvious reason that it wasn't around until 1944 and the Tiger I because it never made it inside the city of Stalingrad. I know this may upset some fans of the Tiger (I'm one of them too) but we're going for historical accuracy here. The only Tigers in Russia at the time were all the way near Leningrad, and there were only four of them. I just wanted to get that out of the way. Anyways, Nezzer's suggestions are great. I'd definitely like to see those in the game along with the Puma that I already mentioned. 
