The problem with a power 3 is that you have to continually give them the ball to make up for what you lose on the defensive end. It worked when Bird played the power 3 because the ball was always in his hands and he drove the scoring both inside and out. Unless the other team's three could score from the outside, Bird had the advantage.
Baby could destroy a lot of those skinny 3s guarding him in the low post. However do you really want him to be the focus of the scoring? Baby can actually move his feet defense but he is still a foul waiting to happen with quick 3s. It wouldn't a good tradeoff unless baby is the offensive focus.
Both Baby and Powe can handle a switch to a quick 3 on defense but not as a steady diet.
The point of all of this is that you want the big 3 to take the vast majority of the shots or speciality shooters like House or the departed Posey. Powe, BB, Perkins, and Rondo can score as part of the offense but not be the focus of it without disrupting things. And with Powe and BB playing the power 3 they have to be the focus to makeup for the defensive mismatch.