If I was to redesign OKW, I would move Stuka into Schwerer Panzer HQ, then give it a fuel decrease like 10 fuel or give it back some cooldown reduction on its Vet.
Then I would add SdKfz 250 Infantry Halftrack
and Mortar Halftrack into the Mechanized HQ. This would allow Mechanized to be on par with Battlegroup HQ (Healing Building) since you would have a way to gain reinforcement on the field and an alternative to the leIG.
Then Luchs/Puma would be available as upgrade in the Main HQ once either Battlegroup or Mechanized HQ is fully upgraded serving as a in between before Schwerer Panzer HQ.
The 250 would require some tech cost reworking to make sense. If it comes to early USF would become pointless as a Sturm in the halftrack could melt the rifleman before snares are even available. The M20 would only be reliable from the rear and bazooka on LT would be mandatory.
If it comes to late it would be a pain to get the 250 to VET1 so that it could reinforce. I think OPEL blitz truck would be a bit better, it could heal 2 units while inside and provide forward reinforce while easier to balance due to lack of combat abilities. IT would make PF and JLI even harder to deal with on a regular basis so maybe a slower reinforce compared to base or Battlegroup.