Hancock- Hancock is definitely a character people hate because of her attitude/personality
And yet there can be so much more about her that we don't know about. How was her before she had to hide her feelings? What were her dreams?
Actually, I think the original Hancock, pre-enslavement, may have been quite like Luffy, carefree and full of big dreams, and she could rediscover herself and her lost dreams by staying with the crew.
and her love of Luffy which doesn't seem to belong in One Piece if further developed.
People seem to think that "love" in One Piece means the series will become a shoujo, with a loooooong shy romance between Hancock and Luffy, with love triangles, three to four chapters with them trying to say "I love you" to each other or with entire chapters dedicated to picnics or dates between them. And then they'll walk around calling each other "my love" and with hands together and do romantic things.
Heck, the "love" angle will probably be played for laughs and resolved off-panel. Maybe in the end they are married or have a child after a timeskip, but I don't see it going beyond that.
Hancock's presence do not need to disrupt the "party" feel of colorspreads. Her "romance" with Luffy wouldn't really change (just add) to the crew dynamics.