I think the Stuka needs a small adjustment of its vet requirements (maybe 10% less). The Sturmtiger also needs to reach vet faster (maybe 20%).
These changes, however, have nothing to do with Volks/shrecks (like many already said).
If you want to get rid of this bad design choice you have to:
- Remove shrecks from Volks
- Give Sturmpios double shrecks for 120MU
- Give Volks Pzfausts (available once the first HQ is built; basically the same weapon Ostheer has for 25MU) + AI upgrades
- Buff the Raketenwerfer (aim time, durability, maybe even a bit more range)
I don't think any other change would fix the problem TBH.
I would rather have a solution that doesn't make Ostheer and OKW early game pretty much the same. Not to mention the fact that the shrek problem would be even worse since it would be even easier to micro a shrek blob then.