I don't know what all should happen but the faction needs to change in such a way that it doesn't have cheap, plentiful mainline infantry units like Volks. The volks were sub-optimal very young and old men. They should be cheap to equip on up front man power cost and require munitions upgrade to get automatic weapons before they can go head to head with any vanilla allied infantry. The reinforcement cost would be higher than conscripts but lower than Gren/IS/Rifles. You might say well they will just get swept away, but in keeping with historical resemblance that they were still well motivated to fight, had some great weaponry (albeit with shortage of all manner of supplies/parts) and had a great corp of capable officers they will get zeal type abilities that can be activated for free with long cool downs as well as have a more powerful obersoldaten with a sturm offizier present in the squad to help inspire the Volks. Read some accounts of the vicious fighting in France prior to and during the Battle of the Bulge. As in the case of Caen, Hitler youth were mingled with SS regiments who had battle hardened veteran officers from the Eastern Front with them who fought tooth and nail for every inch of ground against Sherbrooke Fusiliers and Nova Scotia Highlanders.
https://legionmagazine.com/en/2010/11/murder-in-normandy-army-part-91/
http://www.canadaatwar.ca/content-21/wwii-the-battle-of-caen/
OKW needs to be in short supply of man power and fuel (not munitions as those were more easily made with material from what was available within German borders...oil not so much and because for balance purpose OKW will need reasonable munitions to keep pace) but have great zeal like abilities and a very small corp of elite officers/infantry squads to help bolster their infantry forces. Their armor overall is in a pretty good place. I think we should get rid of vet 5 as it makes units harder to balance and extra vet hardly seems thematic except maybe keep for Volks to represent they had so much room to learn as they were woefully trained/inexperienced.