Real question here. If Bonney does join the crew, what position should she be?
Apprentice is a prohibited answer.
Spy/Support Magician.
Bonney was able to infiltrate Mary Geoise, and can alter the ages of herself, allies, and enemies, as well as futures for a brief period.
Oda has already played into the concept of character classes with Nami in Fish-Man Island when she said she wasn't a Witch, but a Magician.
Looking at One Piece characters from an RPG perspective is very interesting. Franky and Usopp are both Artificers, Franky would have just... so many classes, lol. Brook is an Undead Bard. IDK, I have fun thinking about it.
One issue I see is people act like having two of one trait is bad, like having two lookouts wouldn't make sense. There are plenty of positions on a crew you can double up on, just not obvious ones like Captain or Helmsman. Nothing wrong with having multiple lookouts.