Dynamic Duos

Picture this. A game featuring a duo wherein one of the two protects the other from harm, and the other supports the first. The player plays as the Guardian, and an AI (or second player) picks up the role of the supporter (or visversa, where the player supports the AI). I just realized I described ICO, where the player plays as the Guardian, and must protect the supporter. Only she does nothing but open doors (both literally and in reference to the plot). But I am picturing a game (maybe an RL or an action RPG) where the player must keep their charge safe from the slathering horde of monsters waiting to feast on them. The player is the Guardian - strong and swift, he or she races around the battlefield, hacking monsters to bits and disarming traps (sometimes with his or her face). The AI is the "Innocent", a pacifistic character who weilds powerful magical potential. His or her purpose is to drive the story, as well as to support the Guardian with healing, status boosts, and other various enhancements. Maybe the player should be allowed to choose his or her partner, like an Archer or something like that, instead of being forced to drag around "dead weight".

The new Prince of Persia game has a similar idea, but instead of a guard and guarded set they instead work as one complex character, which isn't the idea I've thought of.