Oda self insert vs a character Oda did not intend to have in the story in the first place.... Kid did not stand a chance. Someone had to be the hype-tool for Shanks. If not Kid, who else? Law? Nah. An admiral? Honestly kinda with Aramaki and the ending of Marineford. Even with that said the only one that can/will merc Shanks in the story is BB.
Tldr: Kidd is irrelevant