The problem is that Iraq is a 500,000 troop problem. Another 40,000 are just going to anger locals... Let me explain why it won't work. It won't work because Iraqis are now politically and socially mobilized. This means that they have the social preconditions for effective political and paramilitary action (they are largely urban, literate, connected by media, etc.) And they are politically savvy and well-connected. They are well armed, gaining in military experience, and well financed through petroleum and antiquities smuggling and through cash infusions from supporters abroad.
The Mahdi Army fighters can be defeated by the US military, as happened twice in 2004. But they cannot be made to disappear, as they were not in 2004. That is because they are an organic movement springing from the Shiite poor, and are the paramilitary arm of a large social movement with a national network and ideology.
Leaving aside aside the firebrand rhetoric about AEI "plutocrats" elsewhere in his essay, I have a grim feeling he's right about the military-political prospects.