It sounds like he's got a lot of things on his side (e.g. confidence, friendship group) - and great that he sees therapy in a positive light enough that he would want to be an SLP! It must be very hard as a parent seeing your child going through that. Yes, Lidcombe is mostly done with younger children but there have been studies that show it can work with older children. I think it depends on the child's personality but if you were looking for a different approach to try it might be worth discussing with your SLP.