That's what pretty much every custom power does, Mal. You decide what you need, and if you can't do exactly that with the powers as given, and it doesn't break the game, make a power for it.
By restricting yourself solely to what is in the book you will be limiting yourself a very large amount. This game encourages player/gm creation of nearly everything- roll with it.
You don't have to define everything according to what is already in the book. RPG's are about creativity and story- not who can jimmy the rules the best to get them to do what they want.
If I can't convince you, fine. I don't need to. I'm sure someone will appreciate having the option that isn't quite so stodgy.
I'm not done with the powers, but I'm certainly done arguing about it, since there is absolutely no reason not to make it a new power. Even if it was completely redundant to another one- which it is not.