I find that attempting to replicate the actual situations during groung combat at a strategic level will be rather dificult. By researching a specific tank technology you get a vehicle that has certain capabilities, ei speed, armor, and armament. What appears to determine what effect these categories affect armored divisions are the land warfare doctrine of specific countries.
From looking at the tech trees for the US and Germany in the demo you can see that the US has a firepower approach where as Germany has mobility. Each doctrine has several layers, all with bonuses to the three categories mentioned above. To be honest, I find that a great new addition to HoI as it allows you to mold your force to your personal prefrences or approach to war, without having to go through the menutia of gun sizes, armor plating, or even command structure. Even Hitler found out it was impossible to keep up with individual tank model production. If any of you have read Guderian's Panzer Leader you will recall the episode with the 50mm guns not being installed on the newer Pz.III's. It did cost the Germans in the early weeks of Barbarossa, but you live an learn. Guderian was himself later in charge of tank development and still couldn't get the production of StuG's or Jagdpanzers to go down in order to use the scarce materials for an increase in the Panther production.
All and all, I think the new system does a good job of replicating the idea of the top, in this case you, delegating matters to various subbordinates. You set the essential parameters, ie. Basic Medium tank or some such thing, and your tech teams come up with competing designs. Whose to say they will always come up with a Pz.IVD before they figure out they can mount a long 75mm gun on the same turret and end up designing a Pz.IVH instead. That is determined by the parameters you set, ie your military doctrine.
Merlin