Incorrect... my direct quote shows: "rare percent chance a child starts training a random skill." Mooding is instant legendary, where training is a very slow process, no artifact and no reason for the player to wall them. It's like building a castle and having one created from a spell... both very different.
Then, what is it adding, in terms of gameplay? A few ranks some skill at coming-of-age? Materials claimed that the player can't override? "Foo Child cancels Train: Went Insane?" Sheesh, skills aren't too hard to come by, and neither are kids, as vanilla stands. I do like the idea of apprenticeships, but that sounds very underdeveloped.
As mentioned before what's currently listed in the future plans does not match exactly what I've suggested and thus the reason to provide a deeper insight into the ideas. Clearly missed by you since you view obtaining legendary status from an event which lasts less than one month is the same as training a skill over the course of many years where the experience would be probably half. Not to mention the mood danger or the artifact difference as well.
Should the developer be trolling endless threads reading all the various discussions to glean the differences between what he has planned and what
you want? Why do you need busy kids?!

My idea is just an idea for consideration... it's mainly a concern because I've read lots of players who have walked away from the game say they're bored and found their last games involved them looking for something fun. I think there's enough building destroyers, but we need something which destroys walls and tunnels thru the earth barriers. Perhaps the tunnelers which destroy walls and earth barriers I mention could be introduced for different game difficulty levels.
Do you think a placeholder should be thrown in now, rather than be built in farther down the line in the Army Arc? You think Toady has indicated he cares that some people might get bored for a while? Personally, it's happened to me a few times. Doesn't mean I won't be coming back. And coming back. And coming back.
And seriously, you realize this has been
done to death, yes?
As a side comment I think vampires are way too common in the world.
Let me introduce you to Advanced Worldgen Parameters,
http://dwarffortresswiki.org/index.php/v0.31:Advanced_world_generation (alas the old namespace)
The trap_avoid doesn't work if the trap has the giant spider silk as described within the wiki. The wiki makes several comments of how powerful cage traps are in the game. Once my game skills improve I will probably not even use cage traps because they feel too powerful.
That is part of the fun! You don't have to do anything, but why worry so much. "Space" is so relative in this game, anyway .... I don't know. It feels silly to quibble.
Naturally 10 dual wielders vs 10 sword/shield wielders of equal skill would have the sword/shield wielders win however. I view dual wielding more as the players rogue who comes from behind to strike for more damage while two player tank units are blocking the enemy attacks from a large minotaur.
"For more damage." So, like, magically? Or what? I mean, this sounds like a needlessly gamey tack-on to an incredible model for combat. And, AFAICT, dual-wielding totally works for adventuring.