Now because we have this cooperative multiplayer mode and we had to ensure that this particular gameplay element was going to be fun, it means it's deeply integrated into the core gameplay.
That allowed us to do something in single player that you haven't seen before (we think). Other than customizing the looks and stats of your party members, you can also customize their personality. That means that if you're playing alone, and you don't want to roleplay both characters, the party member you're not controlling at the time of initiating a dialogue might actually disagree with the choices you make, just like in the example where we had two players control the party members.
As with all new things, at first sight this might sound like folly, but think it through.
Imagine that this would be Ultima VII, and you would have Duprez (a known womanizer) in your party. In our system, whenever the option to flirt would pop up, you could rest assured that Duprez would go for it, even if you might think it'd be a bad idea. If he'd win the discussion, you'd have to deal with the consequences, adding to the fun and potentially showing you a part of the game you'd otherwise not see, because you'd instinctively have answered otherwise.