I never understood why German Army decided to operate two very similar vehicles of roughly the same weight and dimensions in parallel: Panzer III and IV. Instead of choosing ONE common chassis for mass production as early as 1937 they allowed two companies, Krupp and Daimler-Benz, each to build their own tank. When the Stug was conceived by the end of the 1930s, the step to one common chassis was even more obvious.
Since this thread is about engineering: Why no big sloped frontal armor plate on Panzer III, IV and Stug? Instead they opted for this cubic, stagged boxes-like appearance. Although cubic tank design was pretty common everywhere in the 1930s, it involves more metal working while it consumes roughly the same amount of steel which means there are no savings in weight compared to a sloped plate. Besides, a sloped frontal plate in P III and IV would generate a little more space. Sloped armour and its ballistic benefits were known and implemented in armoured cars (Sd.Kfz. 221, 231, etc.) by mid 1930s and even turrets of Panzers have it to a certain extent, so German Army and engineers deliberately decided against it in P III + IV.
Maybe the vertical glacis was a trade off between protection and accessiblility of the transmission. When they started fitting their tanks with additional armour in 1940/41 and cleaned up the ffront plate of P IV (removed the bay window of the driver) they could have implemented a sloped plate. They didn't for some reason. Later, with Jagdpanzer IV they chose differently and in the design of Panther, Konigstiger, Jagdpanther and Hetzer acessability of the front transmission seemed not to be of big importance anymore.
Next point: Germany had large programs to convert their obsolete tanks like 38(t) and Panzer II into tank destroyers (Marder), self-propelled artillery (Wespe) and self-propelled AA vehicles (Flakpanzer II, 38t).
However, they never went for a lower structure like Sweden did with their Stormartillerivagn https://sv.wikipedia.org/wiki/Stormartillerivagn_m/43
Instead Germany fielded tall oddities like the Marders. Maybe installing the cannon backwards (= muzzle facing the back, barrel over the motor section, like the Archer) could keep the size low. Probably this was prevented by German doctrine: 'Tse German driver must not face tse rear!!'.
They could have used the Czech facilities to produce continuously the 38(t) chassis for a self-propelled artillery vehicle or a tank destroyer similar to the Stormartillerivagn instead of stopping the production of 38(t)s in 1942. Mounting a Pak on this chassis with a sloped superstructure would give a more primitive sort of a Hetzer two years earlier. With iterations in design and variants they would probably end up with a Hetzer anyways. Or they would redesign the chassis earlier - if they were better organized.
Or they would abandon the 38(t) and retool the Czech facilities as early as 1939 in favor for a common chassis for Panzers (PIII, PIV), Stugs and self-propelled artillery. One could ask further, why the Czech engineers did not use a sloped frontal plate for their ČKD LT vz. 38. The tank is a clean and nice design and as seen on the Swedish descendant, a sloped plate was possible.
Why no rear transmission in Panther and Tiger I + II? Without the drive shaft going through the vehicle, the tank could be smaller (less target area) and weight would be saved (to be put elsewhere on the vehicle, maybe in more length). With this, access to the transmission would be easier.
Or why has the Panther this superstructure over the tracks (like PIV and the Tigers) with sloped sides like the T-34? A more simpler, mass producible geometry like the T-54 was not beyond means of imagination. Basically, it's just a cuboid with sloped front plates on one of its 6 faces. Panzer III's hull too is just a cuboid with a square angled front plates on one of its 6 faces, pretty similar in concept. Details of the Soviet model like the 'invention' of reverse sloped armor on the sides to adapt a narrower hull to a lager turret ring diameter (Panther 1650mm vs T-54 1825mm) were not necessary at that time.
German Army and engineers never opted for an all purpose vehicle chassis - i.e. tanks, tank destroyers, self-propelled artillery, engineering tanks, etc are based on the same chassis. So by 1944 they had a even complexer mess of different types than in 1941: Wespe (PII chassis), Hetzer (38t chassis), Stug (PIII chassis), Jagdpanzer (PIV chassis), Hummel, Hornisse (PIII/IV chassis) in addition to Panthers as 'MBT' and Tigers as heavies. And were already working on the E-imaginations.
German tank production strategy was a disorganized short-sighted mess.