I mean Luffy might have a battle with him this arc, but I feel like for an extended 1v1, Dragon is a decent bet. He's the Revolutionary Army's leader and I think actually showing his abilities in battle makes sense. Losing to Im makes sense, but I think besting a Gorosei prior to that is fitting. I just want tons of Dragon focus. Then again, Garling is still there, so maybe he could work as an opponent too.
As for Kid, Law and Sabo, they can still battle the other Gorosei and Holy Knights.