That's not really a black ability. Black can pay life to draw cards, but that's worse than blue card draw. I get that this is part of a cycle, so maybe "Reveal the top card of your library. Each player loses life equal to its CMC, then put it into your hand." That way it's really black.

Where does the argument come in on this keyword?

That's a holdover from the previous mechanic, which cared about number of cards in hand. But since Samuel is letting us edit the card set, I should be able to clean that up.

Thanks for the color pie comment, I guess it's not as relevant now that Manipulate is different, so I will edit it.

Untapping isn't really black, so it feels odd that this is a black-tivated ability.
I enjoy the flavor of manipulate quite a bit, but I worry about the inherent power level and possible brokenness. I do think it should be limited to other creatures, just for clarity.
By the way, if I had to choose a color identity for manipulate mechanically, without looking at the flavor of the name you've given it or at the flavor or the set, it would be , not .