I think Roger, Whitebeard, and Rocks pirates have really proven that you need more random bullshit in your crew. Like not just fighters, but people that the captain thought was cool so he had join for no reason. All of them had random kids, cat people, fishmen, mafia, and strange bullshit in their crew.

Luffy should recruit Bonny, Tama, Yamato, Vivi, Wapol, Vegaspunk Lilith, Kuma(revived), and whoever else that was a recent ally into the crew just to shake things up. Bonny's old crew is probably dead by now so she may as well join.