We already know Kage Bunshin isn't the key to this problem. That's why they presented the fusion into the plot in the first place. Maybe down the line Naruto will find himself having to do it via Kage Bunshin, but for the time being, this fusion is the way to make this work.

Maybe that 4th's frog key thing for the Kyubi can come into play now though? Maybe if they get both Ying-Yang chakra's together, the Kyubi wont be such a douche anymore or something. Just seems like the perfect time to make use of it.

And yeah it doesn't seem like Kakashi is quite dead yet. Matter of fact, I think it may be like Jiraya, where he willed himself back to life, except you know, for real, not to just die again. But to be honest, I don't care what anyone says, I don't want Kakashi to die haha. If Kakashi dies for Chouji, I'll be pretty annoyed.