I think it would be fun if there were a few unknown species of wild plants and mushrooms when you start at a new site which could use the herbalist skill to determine if they are good or bad to eat. More skilled herbalists should be better of determining if they are dangerous and not pick them and bring them to the food stockpiles. Cooks and brewers should probably just assume if it's in the stockpile it's good to use.
Random thoughts:
- Having a mix of edible and poisonous would help prevent players from knowing anything unknown is dangerous and just forbidding them. Serious effects like death should be rare for the same reason, negative effects should mostly be minor and temporary. Good effects shouldn't be so good as to have a major impact on the fortress (like everyone double speed forever because of 'juicy stinkcap wine').
- Preferably they have some kind of descriptive names which at least gives a good indication of what kind of thing it is- like 'nightmare berry', 'purple melon', 'sweet leaf', or 'warty cap'.
- Could have different effects if brewed, cooked or eaten raw. Poisonous raw could be edible when cooked for example.
- Negative effects: delirium, dizziness, nausea/vomiting, losing consciousness, terror/fear, rashes, organ damage, death
- Good effects: mood/speed boost, needing less food or sleep, euphoria
- Hidden effects, like deadly to elves but perfectly fine for dwarves, for the fun "why did the entire dance troop just drop dead in my tavern?" situations
- Dangerous foods more common in evil biomes, safe food more common in good biomes. Dangerous ones maybe more common in the deeper layers?
- Different plants/mushrooms found on the surface and the various cavern layers
- Potentially a good thought for something like trying new foods or being adventurous?
- Maybe foods with stranger/extreme effects (like curses or blessings) found in jeweled clusters? What do you do with that single 'shining apple'? Or does it attract monsters from the deep?
- Useful for poisons when those are a real part of the game