(Note - I’ve only played with the official Emotional Attributes).
Giving an Emotional Attribute to a character makes that characters story about that attribute. It may not be the up-front story, but the big picture stuff will totally be influenced and directed by it. It’s also why BWG Orcs losing Hatred when they swear themselves to the Void is so huge - they stop being Orcs in a very real way.
On occasion, I try to rewrite the handling on Need and Despair to make that part of Under a Serpent Sun work. It never works. One of these years though I’ll get it, though I have this sneaking feeling that when I get it working it’ll be based on Mouse Guard Nature.