1. Make the Tiger I tanks constructible from the Wehrmacht's heavy tank building, BUT only one on the field can be released. Basically make it Doctrine-independent.
2. Replace Blitzkrieg's Tiger tank ability with either elite infantry deployment (I mean really elite...like fully upgraded and equipped MP44/Panzerschreck teams), or air support such as a Stuka strafing run.
3. Hm, I want to pick that up. STUKA STRAFING RUN. Should be in the Blitzkrieg doctrine somewhere.
4. Have more unique abilities for each German tank. In example the Panther could need a "stationary weapon" ability, which will increase its line of sight, make it impossible to move. As it was used in the war to shoot down targets from 2000m frequently (and penetrating heavy armour).