I've thought of this before, but only now releasing it to the public. Fallout should have some sort of Age System that allows players to age and grow and gain more experience in the world. Children will grow into teens, then into young adults, then into full adults, and will stay like that for the rest of the game. This will also work for those who are already teens or young adults, and new people will be born into the wasteland. Also, main characters can choose to start off in their teenage years (Around 18 or 17 years old) young adulthood, or as a full grown adult.
And that was my idea for an age system in Fallout. Please leave any comments, or suggestions for future game ideas in the comments. If I like your idea, I may post it in the blog mentioning that it was your idea, not mine.