"The problem is what else they would take care of with those resources."
I acknowledge the difficulties. I'm sure the Kurds will keep to themselves. The Sunnis might be deterred from avenging themselves because they're outnumbered 2 to 1 by the Shias.
The problem I foresee is what would happen in mixed neighborhoods where Shias and Sunnis live in proximity to each other. Flight is the response that's been happening at the present moment. Baghdad used to be a mixed city but currently Shias are leaving it to get away from the Sunnis.
Nothing is going to be 100% effective but I'm reminded of the saying: "...insanity is doing the same thing over and over and expecting a different result". Something new has to be tried. If it fails we did our best. That is how history would judge us.