First idea was for carnivore trait to make players unable to eat raw fruit and vegetables while making them able to eat raw meat.
What's right now in that mod is what Player Model Lib provides as it was the fastest thing to add. I would be happy if there existed an alternative or some implementation of my idea.
As for nutrition system replacement CDDA and forks of it had some good ideas, where food would provide calcium, iron, Vitamin A, B12, C, having too little of each leads to deficiency.