For that to happen a character that isn't part of a crew would have to bond and develop with Law, and that would be no one.
Law only really interacted with the Straw Hats and the villains, there are a few others but none that would be pirate crew candidates.
Your sig makes me sooo sad
Law did interact with Cavendish but Cavendish is the last person who'd want to abandon his own crew (if he even has one) and join another. He likes to be the leader and not be underneath someone.For that to happen a character that isn't part of a crew would have to bond and develop with Law, and that would be no one.
Law only really interacted with the Straw Hats and the villains, there are a few others but none that would be pirate crew candidates.