Penny Arcade has started a new round of "Lookouts" and WOTC has rolled out a 'kids' D&D game so kids games are kind of in the air (John Harper's working on something too and because it's John, it's probably going to rock). The bug has nibbled at me, but I also know that I really wouldn't even take a swing at it until I had time for some massive fictions consumption.
See, the problem is that most RPGs are much more fighty than kid fiction. Kid's stories, especially YA stuff, have a lot of conflict and adventure, but precious little actual fighting, and when there is fighting, it still follows very specific rules. Enemies are knocked down or tripped and taking out of the fight through their own incompetence.
This is why I use the yardstick that a system that can't handle tasers can't handle young adult fiction. Fights in YA tend to be one sided and resolved by clever efforts, not direct confrontation. Boxes are dropped on things, enemies are tricked into traps, oil slicks are spread or (as is perhaps most common) enemies are evaded entirely. 
RPGs don't support this well. They support fights well, and you occasionally get efforts to shoehorn these things together, but it tends to work badly. To understand, take a look at actual kids material. At the extreme cartoony end you may have direct violence, but even that has specific rules - you can only hit appropriate targets (zombies, robots, stuff like that) - otherwise attacks are dodged, parried or blocked. When that doesn't happen and a hit lands, it's palpable and a non-trivial event. Consider that model versus a traditional hit point approach and the disconnect becomes evident.
Other approaches are even more indirect. One reason magic works so well for YA stuff is that it often offers an array of ways to handle problems without violence, and when direct conflict is necessary, keeping it specifically within the domain of magic allows it to be dramatic and forceful, but rarely actually hurt. Similarly, it's very popular to allow for fierce conflict by proxy - cockfighting games like Pokemon allow kids to get their fight on without actually getting in a fight.
You can really go on for ages finding examples of this, but hopefully if you've been exposed to enough young adult stuff, you can see this pattern well enough. Minimize direct violence, emphasize cleverness and other virtues. Easy peasy.
But that's not what RPGs tend to do well, so the prospect of a breakout RPG for kids is a rough thing to pitch, especially when the strongest ideas ('A Pokemon RPG!') are wrappers around things that are already fun on their own. If the idea does not include the unique benefits of RPGs, it's dead in the water, because kids are smart, and they'll just go do the other fun thing without the baggage.
So what DOES make a good YA RPG? That's where the plie of fiction comes in. Start grabbing books from Rowling to Nix to Alexander to anyone else you can think of and start reading them with an eye towards what problems the hero faces and how he overcomes them. You will find that the answer is very rarely "With Both Guns Blazing" but what the answer is may be a bit harder to pin down.
1 - Very, very few can. Insta-helplessness is a cost effective route to killing for bad guys or easy victory for good guys, and most games put up explicit barriers to keep that from being a cheesy path to victory. Unfortunately, it's essential for YA stuff.
2 - This does not last forever, depending on the story. One coming of age element that you'll sometimes see is the point at which the young hero must fight and kill. It's never a trivial thing and it underscores the idea that you don't do it lightly. This idea has, of course, been subverted by the popularity of dark hero tropes, because killing is fun an totally ok because there are lots of people who deserve it! However, that's just lazy writing. Killing people without consequences is juvenile at best, and a number of writing habits have evolved over time to address this. Monsters, specifically unsophisticated evil monsters like zombies, allow for "killing" without complexity.
3 - Yes, it can theoretically be handled by very abstract hit points, but in practice, that theory works for crap.
4 - This is not to say that YA stuff is toothless. It's not. But if you think violence is the only way to bring it, you need to work a bit harder on that.
5 - I am not touching anime in this discussion. Just acknowledging that and moving on.