If someone has the fuel to unlock T4 and build a T34/85 why shouldn't they? If they do it early that means they've skipped all other fuel investments. If the enemy does not take advantage of that then it makes no difference when the 85 comes as the game is already won:/
I agree with this. It is better to tie call-ins vehicles and tanks to buildings than to tie them to CPs, because then you can't skip the buildings. For example tier 3 building for Stug-E and tier 4 building for Tiger, and major for Calliope and Pershing. Maybe tier 2 building for Ostheer Puma and captain for M10.
I also think that Hectors idea is good, that is, nerfing light vehicles by increasing the MP cost for each light vehicle.