Could you imagine if Ornstein and Artorias fought? That would be such a cool battle. And then, later on, you had to fight them both? Oh man, fighting them both would be hell. You could like, fight them both, and then summon them for one boss fight of your choosing. Say, you're having trouble with Four Kings. No problem, just summon Artorias this one time and it's a certified almost win. Having trouble with Nito? No problem, just summon Ornstein this one time for an almost certified win. I would love to be able to interact more with NPCs in DaS2. There was so much potential with NPCs like Beatrice. And to interact with both Artorias and Ornstein would have been really, really, cool.