The OKW PIV has significantly different veterancy than the Ostheer PIV.
Panzer IV Ausf J. Medium Tank
Unlocks the 'Combat Blitz' ability
+60% turret rotation speed, -25% scatter
-30% reload, +20% rotation speed, +10% ac/de-celeration
+12.5% range, -25% scatter
+53.85% accuracy when moving, +45.8% sight range
Panzer IV Medium Tank
Unlocks the 'Blitzkrieg' ability
+30% armor, +40% weapon rotation speed
-30% reload, +20% rotation speed, +20% ac/de-celeration
As you can see the OKW vet gives more turret rotation and reduces scatter by a very significant margin making it very effective against enemy infantry; which is what the Ausf J is supposed to be effective against. It's not something you want to rely on for AT because it's going to have problems versus multiple 85's and especially heavies like IS2's but it gives OKW something to even out the mid game.
For a while now OKW has been somewhat anemic and UP compared to Ostheer due to lack of a non-doc suppression platform that can stick around and lock down area's (The Flak Track and Kubel becoming extinct when AT guns and medium armor hit the field) outside of using their Schwer aggressively as well as the fact they had nothing between the P2 and the Panther and the P2 is dropped in popularity significantly since EVERYONE uses Guards now which directly counter OKW light armor.
Fuss spam is so common because it's much more efficient than getting Obers while Fallsch are to fragile and JLI don't pack enough punch. Personally I would like it if Obers came with 2 StG44's standard and when they got the IR StG44 upgrade it replaced the remaining two rifles. Make the LMG34 upgrade replace 1 of the StG44's.
Volks also should have a anti-infantry upgrade. Why you ask? Because right now Volks literally only exist because they can tote around shrek's. If you could upgrade your Volks for a cheaper price of say; 60-70 munitions, with 3 StG44's after converting your second HQ (regardless of what that HQ is) then it would give a reason to make Volks after minute 10. That or just make Volks come with 2 StG 44's standard at the start of the game but just make them worse than normal ones and increase the price of Volks to like 260 MP.
It's annoying that the faction that's supposed to be all about using extreme amounts of automatic weaponry have more rifle units than literally any other faction in the game.
I really enjoyed reading your faction analysis and your precise identifiction of OKW unit build order dynamics.
Your recommendations to improve things, though, are borderline gamebreaking and require a major overhaul of the faction therefore not really applicable.
I aggree that vanilla Obers are a bit weak now, making the upgrade mandatory, but your suggestions either make them better OH PGs or the upgrades redundant.
You always can build volks since their shreks gives them vet rly fast. Sure, their basically just a mobile shrek platform past minute 10, but therefore quite effective. Giving volks significant AI capabilities would make it almost impossible to deal with OKW infantry in all phases of the game.