Yes, I have every helmet ever modded in my Z under SS, Heer, and Luftwaffe folders (in addition to the CW and US folders of course). You just have to renumber em as high as the number of different mods you want.
The variety is wonderful. But, I was concerned I made a mess with Heer having SS pattern camo helmets and vice versa as I did a lot mixing and matching when the 12th SS mod came out a year ago.
Am hoping that in the confusion of Normandy that the answer is "It doesn't matter, as everyone was wearing all sorts of camo helmets."