Well if Busquets was out, I would support that idea, but he's not and he can handle himself at DM as we know. Yaya, like I and many others have said, is the closest thing we have to Pique. Pique's style of defending and his style on the ball is absolutely perfect for our system, he is god in human form. Yaya has a similar stride, and perhaps a little more pace and his strength and hieght are again the same. Importantly, although Marquez is also awesome at it, he can pass the ball very, very well.
I'm confident that playing alongside Milito, he'll feel very comfortable, Milito is a very intelligent defender, positions himself well and often makes crucial interceptions, tackles and blocks just as Puyol does. We'll be fine with them two at the back.