I'm not saying a Good development program can turn crap talent into pieces but he did get drafted for a reason. So chances are the talent is in there. There's a strong liklihood Harris will fail, regardless of who develops him as thats the nature of the business.
I think there is a much larged advantage to having a good development program than you are letting on though. There's a reason why some pitchers never succeed in some orgs and the Cardinals, Pirates and Indians keep producing MLB players.