What if you could always succeed at foraging (as long as there was a plant present to forage) but couldn't always identify it?
Starting at low levels all plants would have the same generic icon-- a weed is a weed, right?. Each plant would have a difficulty level for identification, if your skill exceeds the difficulty you can identify the plant as the types we have in game now. The generic plants would all be edible, but not knowing what is what you run the risk of getting sick or worse This would be especially fun with mushrooms if/when they are added.
Not sure if it would be better to have each unidentified plant type in its own stack, but with an unidentified "flag" that switches to identified and the proper icon when your skill exceeds the difficulty level, or just stack them all together as a single type with a random effect on eating.
I like your thought process, but I would have to say no to the idea.
I think it would take a lot of work to make a system like that work. The system in place is actually pretty good and seems balanced to me. We kind of have to imagine that identification process going on behind the scenes in the current implementation but it basically achieves everything you are asking for much more simply except one thing: the ability to accidentally poison yourself. Most people are going to try to avoid doing that anyway and many will just avoid foraging completely to avoid it. It would be cool/funny to poison yourself the first time it happened but after that it would be a hassle that you tried to avoid. Why spend effort programming in an effect that would be primarily avoided? There are a LOT of other things that Xsyon needs more.
Besides the prioritization of development resources the idea itself has some issues. How would this work as far as giving food to other people? Would you have to take the person's word on what they were giving you to eat? Would eating a certain plant that someone told you was good help you to identify it faster? Would that make leveling the identification skill exploitable and ultimately pointless except as a way to gain base xp and level health and spirit?
We also have to assume that there are almost always plants around. Allowing players to pluck the literally tons of useless foliage around them in order to get to a tiny bit of useful stuff might just clutter up the database.
It's a fun idea and reminds me of a discussion I overheard in game the other day about that movie "Into the Wild," but I just think it's probably more trouble than it's worth.