Why not just leave? It seems clear that every dollar spent an Iraq will never ever be recouped from the oil there. Unless you count Halliburton and probably Cheney later on.
There is little or no chance there will be WMD in the future since they are likely not there.
Every soldier's life lost there from guerillas from now on is preventable by just leaving, accidents will happen anywhere.
A force can be left nearby in case Hussein tries to come back, that could be handled by air strikes.
Why spend the blood and treasure? Tell the iraqis the soldiers will leave in 6 months ready or not and the attacks will mostly cease.