I think I know what the one piece is
On the opposite side of the coin I think that it’s possible that joy boy and roger chose not to claim it and neither will luffy because they all embody and enjoy freedom the most. And in a way making a wish to choose a destiny is kind of stealing the ability to exist in life at complete random from everyone else. Subject to someone else’s will and dream.
I don’t know if anyone’s done this before, but after watching 1046 I had to try this. Sorry about the quality, I didn’t wanna spend forever cleaning it up.
If momo aged 20 years and became an adult dragon like Kaido, then Kaidos dragon form would’ve looked something like then when he was young