So weaknesses typically take the form of the "Catch" part of the Toughness and Recovery powers. Looking at your presumed build, it calls for +1 worth of catch, meaning you can get by with a very specific, hard to find, and hard to research weakness.
You could easily justify the +1 refund you need with a catch of bamboo weapons and Shinto holy items. In fact I would normally price such a catch as +1 for being difficult but possible to research, and +1 for for being difficult to find but possible for anyone who is willing to devote the time and money. So in my games it would normally be a +2 refund total, but since you are taking a power that costs -2 to get and the refund from the catch can't reduce the power's cost below -1, it is effectively a +1 Catch for you.
God I hope that all makes sense.
As to the question about using magic, Channeling is really just a very focused, less powerful version of evocation. With both you would have to choose the element Air to accomplish what you outlined, but anything you could do with Channeling you could also do with Evocation. So it's not really a question of "which one do I take to accomplish X effect", but "am I someone who has an uncanny ability to control the spirits of air (channeling) or am I a wizard-type spellcaster who happens to be slightly better at controlling air (evocation)".
I recommend channeling for you, as it would fit better (it seems) and is cheaper. Now you have to design a spell which would accomplish the effects you describe, which isn't easy in itself. Give me some time to think about it and I'll post what comes to mind, unless someone else (hopefully) beats me to it.
