This gives me an opening to ask something I was pondering...
Should backgrounds develop, or are they things that happened in the past and there they are? If the later, then should the game award backgrounds as players do things? If you literally save the peasants in the kingdom from the horde of slavers that tried to take over, then why aren't you a "Hero of the People"? If you've spent ten levels of advancement and a year in game time sailing the seas, do you get "Sailor"? If not, what exactly did your (possibly) late teen/young adult character do that was more!?
Straight up I think the background traits are a great piece of design and I wish that WotC had built on them and published a whole lot more of them.
I think they help solve the disparity between casters and non-casters by giving even martial characters a way of impacting the game that isn't gated behind DM notes and rolls on a d20. I would give martial characters an additional background at level 1 (my fighter must have been doing something while the wizard was studying at Gandalf University). Obviously this goes hand in hand with having a whole bunch more available so that characters don't start to converge on each other's background too much.
I would also have a set of post-chargen background traits that reflect great deeds that the characters have done. Call them Legend Traits. Maybe all characters get one every 5 levels. I picture these as sort of non-combat feats in a way - Dragonslayer, Hero of Helms Deep, Ringbearer, etc. Things that have an impact on the social and exploration phases of the game but not on combat. Have you killed a dragon? You can take this trait, and you can always calm or entertain a crowd by telling the tale of your exploits. I also helped kill the dragon but didn't take the trait? OK well my contribution has been lost in the telling and I'm sort of the fifth Beatle, or maybe I just don't like to talk about it.