Those familiar with the history of the Middle East know that divisions such as Gelb proposes are a reflection of Western divide and conquer mode of thought, more precisely of the US right-wing and Israeli lobby position. Gelb's proposal creates more problems than it allegedly tries to solve owing to a lack of appreciation of complex problems, and a single-minded purpose of undermining Iran at any cost to the region, the world, even to the US that cannot possibly benefit from such a reckless scheme.
Those who have studied US-Iraq relations know that there is not one ounce of consideration for what happens to the people who live in Iraq, for if that were the case proposals to destroy the country even more than the US has done in the last ten years by dividing it would not be in any kind of discussion. If Gelb and those who claim to be concerned about Iraq really care, they would try to convince the US government to ameliorate relations with Iran and deal with it in accordance to its current power, instead of trying to find one pretext after the other to have Israel bomb it, or to have drones hit various military and nuclear program installations. As paradoxical as it may sound, the best (meaning cheapest and most beneficial to its own interests) way for the US to secure greater influence in the Middle East is to normalize relations with Iran and forget the old Cold War style confrontation that does not apply, and even if it were tried the cost would be immense.
Facts about Iraq's constitution: