I would absolutely love some First Nation items in the game! I have a couple of Sims that I created to have Native American features and some traditional garb and nice house items would be awesome. Soft moccasin shoes and boots, new lightly beaded hair styles, nice wraps and drapey clothing and some wood, stone and bone jewelry pieces and dream catchers and new statue carvings would be wonderful as well as some traditional pieces.
I know that the Maxis team does a lot of research when they do cultural items so they would most likely reach out to someone in the Native community to get input.
Honestly, I'd love a whole game pack around this culture, I think it would be something quite different if some of the lore was incorporated. As an Occult player, I could see Werewolves working really well on a more "spirit animal" or "spiritual shapeshifter" angle and the Medicine Man being a mystical healer.
You're right though, to do an accurate representation means they'd have to be very careful how and what they incorporated. But to take inspiration from it would be great.