The recent German tank threads have made me re-think, "If someone had the idea in the early 1930s would it have been possible to design one general purpose tank to the job of Panzers III and IV?"
My ideal would simply to build more Panzer IV in place of the Panzer III, which would be armed the 75mm L/48 gun from the start.
However, its more likely that 75% of production would be completed as battle tanks with the 50mm gun and 25% as close support tanks with the 75mm L/24. That is until the T-34 was encountered and production of the 50mm and 75mm L/24 was terminated in favour of the 75mm L/48 gun. It would also be feasible to refit the surviving tanks completed with the 50mm and short 75mm with the long 75mm.
The source I have says that about 18,000 Panzer III chassis and about 12,000 Panzer IV chassis were built for a combined total of about 30,000. If only one design had been built could the Germans have built more than 30,000?