Don't really like the STGs on OKW Offensive Package. Don't see the point or synergy with the whole doctrine. Then again, MP40s weren't that hot either. My suggestion:
With Panzerfusielier having a double shrek option, you have an interesting unit that can either go for long range (G43s) ou AT (Shreks). You don't really need anything either for Volks (MP40s) or Obers (STGs). Both are fine with the standard upgrades.
The ones who are lagging behind are SturmPioneers. I suggest unlocking an extra upgrade giving them some combat boost:
- 5th man veteran squadleader (Obers model), or
- Flamer package, or
- Received accuracy buff
And an ability:
- Smoke Grenade, or
- AssGrens sprint
Pick one from each (any one would be quite sufficient IMO, while not becoming OP), and you'll have a really nice solution that improves your current close-quarters potential rather than trying to reinvent the wheel
G43's are close-medium range weapons with a lesser moving penalty. Ober STG also slightly ignores cover and works at all ranges (but best at close and medium range). I like the sturmpioneer idea though.