My prime interest in military history is armored history. One thing i always noticed while reading armored history books, is how ignored the average German tanker was in terms of requests. Usually, if you read crew accounts of their vehicles, they usually want simpler upgrades like larger hatches, easier access to parts for maintenance, minor crew safety improvements, etc. Usually for the allies, they got it. The M4 Sherman saw improvements mostly in regards to crew comfort, gun sighting, ammo stowage safety, improved suspension, etc.
On the German side, it seemed like crews were usually ignored in requests. They wanted much of the same thing: minor improvements to existing vehicles to make combat and maintenance easier. What instead happened were all of these mad proposals for gigantic gun upgrades, extra armor that put suspensions to or past their limits, or whole new vehicles that didn't really serve a practical purpose. Nevermind cases like the Ferdinand SPG, made from Porsche Tiger hulls that were built despite the contract going to Henschel. Or the building of a whole new line of Panthers that ended up being dumped by just upgrading the existing models with side-skirt armor. Why were so many of these built and sometimes fielded, often against the decisions of military commanders and the government agencies in charge of procurement?
That was a lot of self-indulgent waffling and I apologize, but I was trying to frame the question. What was the military equipment procurement system in Nazi Germany like? I'm specfically curious about armor, but I'd love to hear of any other types of equipment.
Strangely enough for a Nazi Germany topic, there is actually very little scholarship on the activities of the Heereswaffenamt (army ordnance bureau) and its role in the design process. There is certainly a meaty monograph to be had there, but it is also possible that much of its internal documentation was destroyed at the end of the war.
In general, the Heereswaffenamt had to navigate the chaotic and polycratic organization of the Third Reich when considering new tank designs. In this environment, they not only had to deal with entrenched industrial interests like Henschel or Rheinmetall, but also the various agencies for allocation of manpower and resources. The Heereswaffenamt evolved into from the Reichswehr into an organization of trained technical specialists with broad contacts within industry. The system was in theory predicated upon a harmonious working relationship between industry and the military, but in execution, the Third Reich's near systematic disorganization and multiple centers of power hampered the making this system run efficiently. In such a system, the complaints of frontline troops often got bogged up in the chain of command. The Heereswaffenamt's own relatively conservative approach to weapons design and near fetishization of high technical quality compounded the problem of refining existing designs or incorporating hard-won lessons into new designs. Hitler also injected an unstable random element into this process with both interference into the design process and his demands that both the army and industry cut through red tape to meet various production goals. While the role of Hitler in the design process was not entirely negative and often overstated in postwar memoirs, he did actually push for heavier anti-tank caliber guns in the early war when the Heereswaffenamt felt Germany's lighter caliber were suitable, Hitler did little to arrest the systematic dysfunction of the Third Reich governing structures and often encouraged this process by delegating to favorites or adding more agencies to further bog the procurement process down.
For a good dissection of Germany's chaotic and ultimately self-defeating procurement process, Jonathan Parshall (of Shattered Sword fame) did an excellent presentation in 2013 about the deeply flawed nature of German tank procurement.
Hilary Doyle addresses this question somewhat in this video, at 3:25 in. https://www.youtube.com/watch?v=YzQtxgL7x-w
I think your question is based off a faulty premise, however. A review of the publications by Jentz and Doyle indicates that the Germans did indeed make a huge slew of minor modifications within each Ausf. subvariant, anything from changing machine gun mounts to welding new handles on hatches.