- Switch the model on the Schwerer Panzer Headquarters to that of the Mechanized Regiment Headquarters. No gun, no reason to build it outside your base, same cost.
- Add a fourth OKW truck option, the Sector Defence Emplacement. This builds the truck with the Flak gun on it.
- Limited to one, priced according to its power, doesn't build anything.
No free giant gun with teching, but if you pay for it, said giant gun is actually useable.
Problem elegantly solved.