just had a 2v2 with both germans using the ostruppen on road to kharkov. amazing how they could pump out 4 ostruppens each plus mgs and pgranadiers. not to mention halftracks and scoutcars. so i thought "they cant possibly get p4 on time for my t34. nope. this build apparently dont hinder them from getting p4 early. whenever i face germans who know how to use ostruppen, i feel pretty powerless.
The low manpower cost leaves lots of room for other units (like MG42) or fuel caches (hence the fast P4 and the fast T2 strategy).
On topic, I think they should start out with a ~20-30 second cooldown at the beginning of the match, so if you choose them directly, you have to wait a little before you can call in the first ones. This offsets their lack of a build time and makes them flood the map slightly later. If you'd pick the commander after that time, that initial cooldown would already be decayed.
Maybe that cooldown could also just be applied to the ability of picking any commander instead. As in having to wait those 20-30 seconds before being able to choose any commander.
The cooldown between call-ins should also be longer. I also think a longer cooldown between call-ins would be appropriate. Maybe make the cooldown decrease when you have gained a few CPs if this is possible ingame.