All but two SS units had war crimes tied to them, the 9th and 10th Divisions.
They will be implemented eventually. They will be no different than any other regular germans, just cosmetic uniform changes (different camo types and insignia). We will probably refrain from putting SS markings in the official game (due to european law issues), but that doesn't prevent someone from making a skin pack if they really want the SS on the collar/helmet.
Honestly though, the SS aren't that great. Their performance in combat was average at best, mediocre at norm, and down right terrible at times (especially at the beginning of the war, they were slaughtered wholesale in combat). That's what you get with what amounted to poorly trained militia with lots of pretty toys commanded by Wehrmacht flunkies (yep, most of the officer corps in the SS were either die-hard nazis or guys who couldn't cut it in the Wehrmacht officer corps). And don't get me started on the war crimes the Waffen-SS perpetrated....