About 10 minutes into the game, Sturms are largely useless in the anti infantry role (talking solid opponents here). Thats ok though, as infantry combat are not what Sturms are there for to begin with: Sturms need to repair, and most importantly sweep, especially against Soviets. Using a squishy 4 man squad as mainline AT is generally a bad idea already with PGrens, and would be even worse with Sturms. Losing your Sturms is usually a catastrophe, and thats just a risk you cannot run by engaging anything with an AOE profile.
BTW I think they already tried just that in the Alpha and quickly reverted it, and its not hard to see why....
Shrecks would be a possible upgrade. You wouldn't have to get them if you don't want it. You can use your Sturms to repair, sweep etc OR get shrecks if you think it's necessary. Even with shrecks you could still use them to repair your vehicles - even better because they will most likely vet up pretty fast which increases their repair speed.
The mechanized regiment also provides repairing so you don't really need Sturms to work as repair units all the time.
Of course, you had to be careful with them but that's not a bad thing IMO. It prevents people from moving their shreck squads straight up to tanks to kill it or expecting them to solo any vehicles.
PGrens are not mainline AT IMO, you have ATGs + AT nades/Pzfausts for that. Shreck'd Pgrens/Sturmpios would function as support, e.g. preventing enemy tanks from flanking your TD or finishing an enemy tank that is already low on health. I'd never use them to stand up to enemy tanks alone.