Hardnose,
I would say, absolutely not.
First of all, for most Little Leaguers, they aren't even going to play past age 12. So you're going to curb their playing in what might be half their baseball playing experience?
For kids who do move onward and upward, I don't know how you are supposed to tell those who are to advance from those who aren't if they haven't had a reasonable opportunity to play the game.
Yeah, maybe if we could wait until age 18, we wouldn't get hurt. Or, maybe we'd have no conditioning for the task and we'd all get hurt immediately at that point.
To me it's kind of like driving. We all know there are going to be accidents and even tragedies, but we all want to drive and need to drive anyway. Well, if you want to play the game, you have to take the bitter with the sweet, and the risks with the rewards.
Why do so many high level pitchers get hurt? Because they're still pitching. Everyone else either washed out or quit.