Wow, I was searching for something like that a week ago while building the mod list for the new play-through and I would more than happily use this instead of Variety Matters. ;)

I have some crazy suggestions/ideas or maybe rather a brain dump that makes a food simulator from this (I didn't try the mod yet, but I've looked through the source code a little):
- have mod "modes": simple, not-overly complex, complex as hell,
- add lipids/fats (maybe even mono-/poly-saturated, trans-unsaturated fats),
- add salt, it's pretty important for humans,
- add more nutrients like iron, zinc,
- separate carbs for at least sugar (we have mods that add it),
- add debuffs (not only mood) for prolonged too fatty, too carbs heavy diets, maybe treat sugars differently from carbs,
- add diseases support (i.e. too much fat == increased chance for heart hediffs/diseases), prolonged vitamines intake == more resistance for some diseases? See Diseases+ and other disease mods for support/patches,
- add the tastes and some integration with "personality" mods so some pawns like fattier/sweetier/spicier/etc. foods (it could prevents things like: "I've figured out these three meals that fill all the nutrients and fill the variety" so I call it a day),
- animal support,
- race support, i.e. some races don't need to eat specific things, don't eat fats, have problems when they eat fats, etc.,
- some cooking/bill/meal QoL, it would be pretty hard to balance the nutrients with how cooking works right now,
- ^ maybe some customised meal system? Have a GUI to select raw foods, condiments, select the graphics, set a name, have game calculate appropriate cooking time on that basis,
- ^ dynamic price calculation, so you can have a shop/restaurant with gastronomy where you a meal with shrimps is more expensive than lets say salad with tomatoes, onions and salt,
- proper mod integrations with Vanilla Cooking Expanded + popular modules, VGP + popular modules, Animal Foods Extended, and others, it would be nice if these could be done on that mods side, so we get proper updates when they update,
- add condiments and a support for mods that add them,

I also love MC mods adding such mechanics so maybe you could check for some interesting interactions there:
https://www.curseforge.com/minecraft/mc-mods/diet
https://www.curseforge.com/minecraft/mc-mods/nutritional-balance

Also Space Haven game has this mechanic too, though quite simplified.