The major reason for not endorsing action on Pakistani soil by foreign forces is that it would be a blatant violation of Pakistan's sovereignty, and would provide propaganda fodder to the extremists, therefore complicating the war effort.
It's only a violation of Pakistan's sovereignty if Pakistan does not agree to those forces operating there.
I don't know the exact reason the Pakistan army pulled out of Swat, but it's quite clear that the army was having some real difficulties up there.
The question is which do you want more - your pride or the Taliban out? If it's the latter, then you can not hold back - it has to be all out war against the Taliban. And if that means enlisting allies to help, so be it.