All Ostheer needs is a 5 man squad upgrade in the late game (maybe tied to BP2/BP3), and some sort of squad spacing fix. All their support weapons are good enough, but not enough to save grens from getting roflstomped lategame by superior allied inf. Maybe some adjustments to their tanks too, namely P4 price/penetration, Panther moving accuracy/reload speed, and Tiger frontal armor.
That, or nerf allied infantry scaling/bullsht double weps.
That's it. All your other points seem to be a non issue honestly. Anymore than what I said above would be overbuff, and it'd be imbalance yet again. My points mostly affect only the late game parts of Ostheer, which was turned into a joke since the Brits arrival and the WFA's power creep.
I wonder what effect on gameplay giving Grenadiers Merge would have...
Merge on a 4 man squad
. also lol at katitof actually taking that seriously.