Now, New Vegas gave us a clean slate protagonist. He/she has no background and you are just dropped into the character and go on your adventure. I had a though ever since they put traits back into fallout New Vegas. I think in future games that have a clean slate protagonist they should introduce "Background traits."
Background traits would let you define your characters back story through game play with a new traits menu. It would be separate from regular traits, but still function the same by having bonuses and drawbacks. You could only pick one of course and it would be completely optional like traits. Again this would only work with clean slate characters like the courier, but i think it's an interesting idea.
Here are some ideas i had for backgrounds.
Vault dweller: you've spent most of your life in a Vault-tec vault. Spending your young life surrounded by the technology of the old world your aptitude with such things is significantly increased, but the outside world is daunting to you and you haven't been prepared enough for life on the outside.
Background abilities: Perks with science or medicine skill requirements have those requirements reduced by 1/3, Perks with survival skill requirements have those requirements increased by 1/5 up to a maximum of 100
Tribal: Living as a tribal in the wilderness has honed your ability to live off the land and skill with primitive weapons. Your upbringing has left little opportunity to socialize with the more civilized people of the wastes, you are seen as barbaric to the more civilized wastelanders.
Background abilities: Melee weapon attack speed increase 10%, throwing distance and damage increase 10%, all Speech and Barter check requirements increased by 10.
Caravan Merchant family: You grew up learning all the tricks of the trade and dealing with all different kinds of people in the wastes. The one thing you didn't learn, though, was how to properly handle a weapon, any weapon.
Background abilities: Perks with barter requirements have those requirements reduced by 100% and all reputations start out accepted. any weapon you use will deteriorate twice as fast.
So, good idea? bad idea? ugly? if you like put your own background trait you would like. I refrained from putting any faction related backgrounds like NCR citizen or Legionnaire, because that just seemed like being able to pick your faction early, maybe in a game where those factions aren't big players.