I honestly don't know the answer to your question, I'm just stating my opinion from an experienced point of view of spamming trenches and just manning them with Osttruppen but like I said, every time there is a tank in my front yard I need to march them outside and hope to god they don't get all one shot to faust the damn thing and then get them back inside.
If a Panzerbusche upgrade is added it could just be made so they wouldn't be able to use the Panzerfaust or upgrade to the MG42 anymore.
If the upgrade entirely replaced the MG42 I don't think it would be that bad either but it's up to the balance team really, I don't mind it either way as long as I don't have to march them out of the garrison, faust and then march them back in.
Your really use trenches, and if you fill them with Osttruppen?? You should't do that. Osttruppen benefit of the distance between the men and the quick refresh rate. Put them behind a sandbag-wall and build as quick as possible a HQ-bunker or a Sdkfz. 251. If your enemy isn't a soviet, or you know he will not build a M3-clown-car, don't build T1 and push in a new Osttrupp instead or build a MG42 (normally a HMG42 is the biggest enemy of Osttruppen, suppression is bad for Grens and way worse for Osttruppen DPS). Better build a 222 or a PnzGren with Schrecks if you need a AT.
Osttruppen only have 1 weapon-slot, why not:
T3 2*Panzerbüchse39 for one slot.
T4 1*HMG42 for one slot.
Edit: The new Defence-Commander is the better Osttruppen-Commander, because it fills the lack the old one has. The 88 is an option for late-game, while the classic one simply has no options. It also needs a revamp (while the revamp happend is really bad… made of people don't play Osttruppen):
1. Giving Osttruppen non-doc sand-bags would be first thing.
2. Giving Osttruppen a upgrade for 2*Panzerbüchse in T3, in T4 a HMG42 upgrade.
3. The trench-ability has to be replaced with hull-down. (since the trench-ability of Defence-Commander was changed with Bunkers, tank-traps and treches).
4. The air-drop can be removed with a Beute-T34/76, a call-in tank.
5. Instead of air-drop give them a Beute T34/76-call-in with T3 (Limit to 1). Also the Panzerbüchse-Upgrade could be locked behind T3.
-Osttruppen
-Artillerieoffizier
-hull-down
-Beute T34/76
-Gustav