AD is probably the best option we have internally for the position, but someone in the coaching staff has to stop believing his own press. Before he can develop he needs to understand how limited his 5/8 skill set is. Only by understanding your shortfalls can you knuckle down and focus on addressing his positional play.
If he really sees himself as a 5/8 he needs an honesty session with a quality 5/8 that can focus on him over the off season. He currently does not read the game well or quickly enough; this stifles the outside attack. If he thinks he is about using his frame to break the line and offload he needs to start watching Jake over at Manly and get a job as a second rower outside of a quality 5/8. His size and strength are only the hammer in his toolbox.
To be the complete tradesman he needs some more subtle tools like being able to read the defensive decisions happening in front of him and then knowing when to pass early and when to go late and short, how to earn repeat sets on the line and when to commit in defence and once he has mastered those move onto some precision tools like landing the ball from a kick on the chest of an outside back, a long passing game, and when and how to roam.
IMO, at the moment, he is a great A grader as a 5/8.