If you haven't I would suggest a look at the Sturmpio vet bonus's because that + 2 shreks = fun times for Allied players.
The fundamental issue for OKW vis a vis shreks is that they are a crutch because OKW lacks plentiful mobile AT. The Rackten is the least durable AT gun with less pen than a ZiS.
This doesn't even touch on how boring just making Volks gren's 2.0 with an AI upgrade + fausts would be.
Nothing special about their vet bonuses.
Sturms with 2 shrecks will definitely cause fun times for allied players since they'll lose their weapons pretty fast if you just blob them like Volks or use them to chase tanks without any support.
The Raketenwerfer has exactly the same pen values.
It wouldn't be more boring than their current state that just causes blobs of shrecks.
Volks without shrecks would result in more combined arms play and less blobbing.
I didn't even mention an AI upgrade.