Some of the animal diets seem... Illogical.
I got a dog which when is REALLY hungry steals fruit from the kitchen, and eats them, and later doesn't feel sick or anything.
Sure he would prefer meat, but if hes really hungry he doesn't really care if its meat, fish, fruit, or chocolate.
So my suggestion is that the diet of all races is expanded onto:
Secondary Aliment: (Gives less energy or may cause small debuffs)
Never Aliment: (Gives debuff)
Dogs Main Aliment: Meat
Dogs Secondary Aliment: Fish (Only gives 1/4 of the energy)
Never Aliments: Everything else pretty much.
Obviously, a Dog can eat a plant, sure he wont get any energy and may have a small debuff, but if he for example tries to eat a Lava Crystal, he would burn down, and if he tries to eat an Ice Crystal, he would get a big debuff that slows him down and causes some damage.
That also opens new gates for spells and adaptation: For example, maybe every time a dog with full energy dies due to burning for eating Lava Crystals, theres 1/4 chance he becomes a Hell Hound.