IMO OSTR should be buildable from HQ, seems rather pointless having them build from T1, right next to grens with a 40mp difference, if OSSTR is buildable from HQ, it will still come out useful, and the early choice between mg ''spam'' or OSTR spam
From patch notes:
"Osttruppen have been moved to the Infanterie Kompanie. Previously, the unit allowed for very potent tech rushes into either Panzer Grenadiers or light vehicles that certain factions had issues responding to. Their panzerfaust range has also been reduced due to their larger squad size over Grenadiers while slot weapons given to Osttruppen will now deal more damage when the unit is in cover. The latter should improve the mid-late game performance of Osttruppen"