Classes with scaling customization sounds like a pretty interesting concept that has not been explored before.
Basically a new player/player with little interest in making lots of decisions during the character creation process can opt to stick with a "core" character, similar to a build in Player's Handbook (or an archetype from Shadowrun), while others can make a few more choices similar to an Essentials subclass, and so on and so forth until they are customizing every aspect of their character like a "normal" class. The best part is that no matter how many decisions you make--or don't--each character would remain viable throughout the entire game.
Pre-packaged characters would also be handy for pick up games, Encounters, one-shots, delves, or players that have their character killed off and need to roll up something quick to get back into the game before the night is over--and after the game is over I'd allow the player to map out their choices in more detail after the fact to get the character they want. There is also talk of making races into classes to evoke archetypes, such as "dwarves" as super tough fighters and "elves" as multiclassed fighter/wizards.
The big question is whether or not this new type of class design requires a new edition? Builds have been in 4th Edition since it was released, and Essentials subclasses were partially a step in this direction in that they dole out class features at specific levels. I think that WotC could pull this off without ushering in 5th Edition, but we will have to wait and see.