Like a Dark Souls, or Borderlands kind of system?...I agree it would be great if more RPGs implemented a system like this.
Maybe in DA, you could have one companion who is kind of a blank slate, that is always with you, a servant kind of character, and a friend could join your game and control that character?
Yeah like borderlands, or even dead island where the game you play co op is recorded to your own profile so you can continue on your own.