If reward cards suddenly stops existing they are limitless pool of resources.
Huh?
But you do have a point Smokaz. Regardless if the company was limited with just 1 Heavy tank, it wouldn't mean the rest of them would be mediums. No they'd rather get more pop cap efficient vehicles because what a medium does a heavy does better. For companies like Blitzkrieg and Armor (the two heavy tank capable companies) players would go for tanks that compliment either Tiger or Pershing rather get mediums. Some might build their companies on both principles but I predict that they'd realize the error. (Even if what works with heavy works as well with a medium, the question is supporting one or all).
It stops the issue of several players fielding something like 3 super pershings and 3 normal pershings, or 3 kts + 3 tiger ace (nightmare).
But, we will need to make tiger and pershing a t2 unlock if you can only field one of them. They aren't that good that they deserve a t3 unlock. I kinda feel the same for the KT, since it just isn't that capable.
Also, like you write, they might go vehicle spam. But vehicle spam is out of control atm because people have become good at building companies.
Light vehicles are probaby the unit type which needs a pool.