OKW has a similar problem to old USF: it's stuck in T0 for a very long time, forcing it to spam out a load of infantry because it has no other option.
The USF overhaul solved this by lowering the initial teching costs to give USF access to a greater variety of manpower based units sooner, while adding sidetechs to preserve vehicle timings.
So here's what I've got:
SwS Supply Truck
- Convert To Battlegroup Headquarters is now free.
- Convert To Mechanized Headquarters is now free.
- Convert To Schwerer Panzer Headquarters is now free, and does not require another truck set up. The flak gun starts disabled.
Battlegroup Headquarters
- New upgrade: Activate Battlegroup Headquarters (200 MP, 25 FU).
- Unlocks the IR Halftrack and Flak Halftrack.
- The medics upgrade is now a prerequiste to reinforce from the Battlegroup Headquarters.
Mechanized Headquarters
- New upgrade: Activate Mechanized Headquarters (200 MP, 45 FU).
- Unlocks the Panzer II Luchs and Puma.
Schwerer Panzer Headquarters
- New upgrade: Activate Schwerer Panzer Headquarters (200 MP, 120 FU, requires one activated headquarters.)
- Unlocks the Panzer IV, Jagdpanzer IV and Panther.
- Enables the flak gun.
King Tiger
- Requires three activated Headquarters.
Obersoldaten
- MG34 upgrade requires Activate Schwerer Panzer Headquarters.
It's a lot of text, but in practice it's very simple: the trucks only cost the 100 MP 15 FU the truck itself costs to set up, but all they can do is build their manpower units. They've then got a USF-style sidetech to unlock the vehicles.
This means OKW can potentially build a tech unit as their third squad. They even have the option of going early Obersoldaten (minus LMG34s) if they're willing to spend 100 MP 15 FU to unlock just them and have an unarmed Schwerer Panzer Headquarters on the field for a long time.
A secondary benefit is Mechanized OKW builds can now get medics for 250 MP 30 FU, rather than the 450 MP 40 FU it currently costs them, and Battlegroup builds have much cheaper access to the Walking Stuka. Hypothetically, you could rush a Stuka 45 FU faster now too, but you'd have nothing but Raketenwerfers and Volksgrenadiers to protect it.