Is there an example of ethnic cleansing being done in a peaceful manner?
And if the number required is a million troops and trillions upon trillions of dollars?
Without even talking about other countries being involved (which will happen) lets look at Iraq itself. First off realize that you cant neatly put a neutral zone between sunni and shi'ia communities. And why would the future Shiite states give their oil revenues to the Sunnis? Further wtf happens in Kirkuk if there is already a strong movement to de-Arabize the area when it becomes clear there is going to be an official split into 3 countries?
No win situation no matter what happens and has been since the second Bush decided to invade.