I disagree with this whole "you should make it a teenager because that's the main audience and they can identify with the hero" line.
First off, that audience demographic has changed considerably. Players are now not overwhelmingly male, it's much more even than it was. And there are now many, many players who are not in their teens.
Second, and more fundamentally, are people really saying that teens are so lacking in imagination that they cannot identify with a protagonist who is not very like them? That has not been the experience in literature, nor in games. Sure, there's plenty of lazy writers who churn out stuff, books, games, movies, which don't require any leap of imagination, but that is a reflection on them, not their audience.
For example, in my second game, which has sold very well, the main protagonist is a man old eniugh to be married and have an infant son. In my last game the main protagonists were a black woman computer engineer and a fairly seasoned journalist caught up in time travel. None of the people they team up with is a teenager and that is selling well too. So how to explain that if it's teenagers wanting to identify with the heroes?