I wouldn’t wanna play as a kid, but I suppose it would be alright as the tutorial (like FO3 did)

Fallout 3 was the only Fallout game where you start as a child so its not a Fallout thing its something Bethesda decided on which means however unlikely, it is not outside the realm of possiblility they would do it in a TES game. (Though i doubt they would).

I pesonally would hate to start as a child or even have a mapped out past, part of the greatness of TES games is the fact you can make up your past, it isnt clearly defined, i really expect it to stay this way.