Look at Senor Pink. He could've just been a silly joke character. But he gets a beautifully tragic backstory that proves he really is manly (in that a real man is willing to sacrifice everything, even your dignity, for those you love)
It will never happen, and I've made my peace with that, but if I could tell Oda to change anything, I'd like Yamato and Katakuri to join Luffy.I like the idea of them rejecting their shitty parents and joining a real loving family.