"Pro guys would be discouraged of this and many have realized the negative of it on their own as a result of an injured shoulder, wrist, and or hand."
No disrespect intended, Dana, but pro guys are discouraged by MLB organizations from doing all sorts of things that would benefit them. And the inverse is true too, that many MLB organizations use training ideas and techniques with no transfer to performance at all. For the life of me, I can't understand why there's still a video on Youtube of a strength coach working with Hunter Pence doing squats on a Smith Machine.
Heavy bag drills can be used in a variety of ways to train young pitchers and hitters. Not talking about going three minutes rounds, throwing combos, and dancing. I'm talking about purposeful drilling using rep/set construction. For example, when working with a cross hitting kid (Throws right/Bats left), I found that teaching him how to throw a low hooking cross with his left while standing southpaw was a great cue for maintaining a solid top hand. Top hand can be a problem for these types of hitters.
And don't get me started on the over half of MLB that discourage something as simple as long toss exceeding 120 feet during the season.