Oh, I totally understand where you're coming from. My DS is a baseball lover and aspires to be a MLB player (yeah, right). But, we encourage him just the same. He's got a lot of the issues you talk about. Having poor form and muscle weakness is a double whammy. Because of DS's muscle weakness, it crucial that he have good form/mechanics so he can capitalize on the muscle strength he does have.
My DH has become steeped himself in baseball 'mechanics' - which is what throwing and hitting are about. He's worked with DS to get those right, including videotaping when DS hits/throws and reviewing it with him to see where he's got bad form. DS has improved tremendously because of it. Same thing with hitting. We got a 'batting trainer'
http://www.amazon.com/SwingAway-Bryce-Harper-Hitting-Machine/dp/B007MOJT7C/ref=sr_1_1?ie=UTF8&qid=1441900325&sr=8-1&keywords=bryce+harper+batting+trainer . Again, DH video tapes DS while he's practicing and they break it down. DH also videos him batting during games. When DS gets nervous (like when he's batting in a game), he forgets 'technique'. DS does a lot of practice, practice, practice so he has more automaticity in his actions.
Don't think we're trying to mold a star athlete! We're not! We aspire to average in this and so many other things. DS just loves baseball and wants to be more proficient. I can only imagine what an awesome player he'd be if this were where is ability was. At least he has a passion.......