Which is exactly what's happening now. Kids who want to fly high power _can_ do so. Lack of certification is not stopping them.
High power certification is not a "formal recognition" of an accomplishment. It's a form of permit which allows adults to purchase and use high power motors. Kids couldn't purchase those motors even if the certified, so it wouldn't help them in that regard. And they can fly without certing, so the lack of a cert isn't stopping them from engaging in the hobby. So what's the fuss all about??
It's been argued that junior certs would encourage more participation by minors, but that makes no sense at all. Creating a special "junior cert" program for minors would actually have the _opposite_ effect, because it would impose a new impediment that currently does not exist. Instead of simply getting an adult to buy the motor and sign off on the flight, they'd have to jump through the hoops to get certified -- and then they'd _still_ need an adult to buy the motor and supervise its use.