A 7,5cm PaK could be made a global upgrade.
German PzIV and Stugs would have short barrel guns untill this expensive upgrade (200MP/80-100fuel) is done.
Pionieres could then build PaK 7,5cm emplacements. 310MP/15fuel
Slightly less firepower than a 17lbs.
Without this upgrade germans would have to fight with shrecks PaK 3,7cm, and PzIII (50mm gun).
This would be historically accurate.
You could risk trying to win a quick lightning war with PzIII and early PzIV or wait for heavy guns.