The BM of the straw hats, his defense drops depending on emotions
I wouldn't call it emotions anymore, it's more about resolve and willpower (which is also tied with emotions, but calling it emotions seems too superficial)
The cool thing is that this is exactly what has been motivating Sanji to get stronger anyways, so it fits his character like a glove.
Once he decided to destroy the Raid Suit and claim he needs to beat Queen by himself, that already is a sign of resolve that forces him to get stronger somehow.
This is basically the "shonen asspull power of friendship" that makes sense and is actually well written, so it doesn't feel like an asspull.
And the premise Haki is all about resolve and willpower anyway, so it's a win/win situation. Anyway, need to see more of this stuff to be sure of things