His rebounding will be OK at the level he is at now, no matter what I would go with some One-on-One forwards. He will get much needed pops in driving and handling (about one every two weeks) as well as jump shot and inside scoring (about one every five weeks with a IS popping a little quicker than jump shot).
I would do One-on-One forwards for 5-8 weeks and then focus on getting that outside defense up to a 9 or 10 after that. From there he could go with more inside skills and make a SF or focus on outside skills and develop a SG.