I'm not sure about the teching costs, but wouldn't that favor the soviets as they only need one building for everything compared to two tech-ups (+ T3, as you would probably need that)? Shouldn't it just be T3 or T4 building for any faction to be able to call in tanks (or just build them in these buildings)?
I don´t think you need BP3 - T4 or even T3 built to get a Command Tank - Puma. While i think the cost for heavies should be associated with BP3.
Cost of teching could be decreased while the building itselft could get a bit more expensive if the disparity with soviets is too high.
All of this thinking with the current performance of callin tanks. This would aim directly at things like:
-TA
-Heavy T2 because you are on the back foot into Tiger
-Zis gun into KV8-IS2-ISU
-T1 +/T2 into T3485s
-T1 + T2 into Elephant. Eventhough on 2v2 it´s feasible on an even game to just get T3 and a 1-2 tanks and then get an Elephant.