*Out of the Abyss Spoilers Below*
----------------------------------------------
In my group's OotA game Stool (myconid) became a playable NPC while the group was trying to take him home and the group LOVED it. However, it wasn't so much the idea of plant-related abilities that attracted the PCs to the idea as it was his attitude and the myconids' storyline intrigue that really endeared the mushroom-folk to the group.
As a GM I think this could take away or put a new spin on food/drink consumption, advantage to certain statistics when in bright light, disadvantage when in darkness, vulnerability to fire and electrical damage, and so on. This would be a fun idea for players and (provided that I saw the stat changes so that I could try to forecast the impact to the overall game to ensure it wouldn't be disrupting) I would most likely approve and incorporate.