Sounds cool but not sure about having that as a particular mechanic only for rogues. Seems like something I'd like to see for other classes as well. Could call them different things for different classes. Schools for wizards, for instance?
I hope not.
I prefer it is more like rogues just get half a background and half a theme as a bonus. The skills and feats still exist in other themes and backgrounds.
Rogues just start with 5 skills, 2 traits, and 2 feats.
Everyone else starts with 3 skills, a trait, and a feat.