Right now we have a 2 item interaction system..that is only one item can be used with another.
It would be interesting to see if you could make a 3 way item interaction thingy. Like you have flour. You mix it with water. It becomes dough. You use the dough on a fireplace. It becomes bread. Heres the fun part..you need to check the dough at regular intervals...if you dont the bread may burn and be unfit for eating!! It would be nice but it may be asking too much of Larian.
Also(becuase im reading Hary Potter) It would be nice to have books which help you make wierd and funny potions(not necesserily for combat or to help with on quests) but a potion like "orc head" where when you drink it all friendly people have an orc head instead of a real head(you still cant attack them though without losing reputation).