Exactly....it would be epic!!! If Robin fought with more of a killing intent she'd be really scary!All of them should learn Busoshoku Haki, that would make them a lot more deadly. But yeah, that Robin thing ain't bad. I can see her hovering in the air, then rain down thousands of Shigan fingers! That would be awesome, and an epic attack. I don't really know what Zoro and Brook should do, since it's not a Devil Fruit. One thing I can see Brook do, is being able to possess people, would love to see that!
And Brook should deffinatly do that!!! He'll get caught because he will try to use a Skull Joke, but realize he does have a body XD!!!
Zoro will probably have an increased arsenal of sword techs in addition to his supped up regular ones (Lion Strike already cutting through a dragon head)!