I'd say he's about barely-14 in this.
I've had a bit of a fanfic idea floating around for a while. Typical What if/What then scenario, gist being 'what if Aang was found sooner?'
It's not the ONLY AU fanfic I have in mind, but it's the one I'm doodling on at the moment. We'll see what actually gets written or drawn from it.