The walk up drill would definitely be a good drill. Also go back and look at the video. Watch the feet- look at them during the set up and throughout the swing. What do you see? Bluedog as usual made a great point about torque and stretch.
When you put your swing out there for others to critique you need to hear what they think. There are alot of kids out there than need to hear the truth and not what they want to hear. I dont see it as negative I see it as positive. Now at least it gives him something to think about. Now he can say "Maybe I need to go get some serious instruction".
When you go to showcase after showcase and tryout after tryout and you continually see the same things in young hitters you start to wonder. Who the hell is teaching these guys?
Then you see the guys with proper swing mechanics and you say "If I were a kid standing here and I saw a kid mash like that I would want to know why he can I can not." Maybe its time someone told it like it is instead of sugar coating it all the time.