UN Trustees for Iraq: US and UK
Once the Saddam-ite regime is completely defeated, the US and the UK will endeavor to find a way to restore it to Iraqi rule that is at once acceptable to them, to the Iraqis and to the international community at large. Cutting this Gordian knot can be done, but so far, the obvious way has not been mentioned -- a UN trusteeship with the US and UK as joint trustees.
The difficulty is that this is a direct violation of Article 78 of the UN Charter; however, a temporary dispensation might be given by a unanimous vote of the Security Council. If it is not called a trusteeship, but still acts as one, the effect is the same while the law can be observed. Diplomacy is about such finesse.
Nonetheless, the US and UK are the only countries in a position to do anything near-term for Iraq as they control its territory -- they must be the trustees. At the same time, the UN is given a supervisory role, letting the French, Germans and Russians save some face, while taking the militant Muslim heat off Washington and Whitehall. And above all, the trusteeship system ensures that an exit is built into the arrangement that will make sure the occupation is not a conquest, something all sides agree they want.
Finally, the Trusteeship Council is made up of the Permanent Members of the Security Council. If they are forced to work together to fix this mess, it could bode well for the entire international system.