Alan Ritchson's role
Recently Ritchson had confirmed his character name as Agent Aimes, a ridiculous but cool name. No details about his character but I guess he's either one of Mr. Nobody/Little Nobody's agents who teams with Dom or he's on Cipher's team, Vin Diesel recently posted a video of himself and Ritchson inside a cargo plane so it look like Ritchson is an ally to Dom and his team.
Video: https://www.instagram.com/p/Cg5DC9TJSa5/?hl=en