The article seems to make sense from the security perspective. That is, if your goal is to eliminate AQI and the local Sunnis won't trust the mainly Shia Army, let them form a Sunni militia to do it. However, doesn't this cut against the central COIN tenant of establishing the legitimacy of the government?

Maybe this is indeed necessary, but this path would seem to ultimately lead to, as the author indicates, a partitioned Iraq. If memory serves, imperial powers tried the militia option in the past and found it quite difficult to turn them off once the immediate threat was defeated. Certainly we would see the same thing as I think the Sunni are not likely to lay down arms once AQI is defeated. Wouldn't they come to view these militia as indispensable to their security since they don't trust the Shia?

The whole thing seems rather circular to me: we have a problem and a proposed solution; that solution leads to another problem which leads to another solution which, in turn, leads us back to something similar to the initial problem. I think I'm beginning to understand the soup with a knife analogy. Anyone care to shed some light?