I’m starting to feel like you think more AS Carrot than the actual (completely fictional) character herself…seriously, this is deeper thought and consideration about her journey than absolutely ANYTHING said to, by, or about the rabbit in any given panel or scene.
And still, everything I say is teased by the story.
It's all over the floor in front of you. I'm not giving random ideas here, but a logical narrative potentiality teased by very subtle elements in the story.
Carrot joining is not supposed to be obvious. But it's supposed to be logical:
Carrot joining for fun.. just to being scolded about the danger of the seas.. to actually experience the terror of the sea.. and wanting to get revenge for it just to lose again in front of that terror... Is very logical narratively... but also..
Psychologicaly!
It's the logical cycle of a coming of age story but twisted on it's head. The actual refusal for adventure that should come at the beginning of the story will actually happen at the very end (or rather the end of Wano), because that refusal is the BIG choice Carrot will have to make in front of her own weakness.
Nothing is invented here, it's just pure narrative logic.
Oda's goal was simple and don't needed a lot of exposition: Carrot needs to doubt herself and accept death as a part of her journey.