The same way the Russian doctrines allow you to play different times and situations (Urban Combat= urban combat, Propaganda= early Soviets, Armored Breakthrough= late Soviets), I think the Ostheer should reflect different times and situations for the Wehrmacht in the Eastern Front.
Basically, you could make a skeleton of the faction based on a mixture of Wehrmacht and Panzer Elite, and add units and abilities to really drive the point in.
For example:
Early war Germans could have access to huge artillery support and sneaky troops, while suffering from a lack of AT capabilities (they would use PIV ISTs instead of Panzer IVs). They would have a harder time reaching heavy tanks like the Panther.
Middle war, they could have access to the regular PIV, as well as normalized costs for heavy tanks. They lose artillery support and sneaky troops, but they also gain access to specialized assault troops, something like the Soviet Ingenery with upgrade (satchels and flamethrowers). To make them different, you could remove the armor but add fire-up or greater suppression resistance. Except for the one flamethrower, you could have MP40s.
Late war, they lose a lot of offensive capabilities and still have no strong arty, but they get ambush defenses instead. Ambushing Marders, ambushing Volks, cheaper mines and trenches. The ambush for different units could cost command points and work in progression (2CP= Infantry ambush, 4CP= Light Vehicle ambush, like Marders and Armored Cars, and 6CP= Ambushed tanks, like PIVs and Panthers). In this case, the Soviet player has a lot of good reasons to send waves of infantry in first, just like in the late war. Also, you get a lot of infantry with cheaper faust uses.
