This would provide a perfect cover for al-Sadr's escape. It would flood the holy city with non-combatants, forcing a ceasefire.
It would, however, end the specter of the "abomination of desolation" that the Gospels spoke of. I'm not subscribing to any theory of Christian endtimes here, but only pointing out a useful paradigm. The Gospels report that Jesus warned about an "abomination of desolation" which would signal Christians to leave the holy city of Jerusalem. This is best identified with Jewish militants taking over the Temple complex in 70 CE. Rome had already surrounded the city - they allowed people to leave if they wished. Then they obliterated Herod's Temple.
The same flag should be a signal to us today. When militant religious fanatics take over a holy shrine, things are going to get ugly really quick. America doesn't have the option of the Roman solution here (and such a solution should be forsworn anyway). This may be the only way of getting al-Sadr out of the mosque without igniting a devestating civil war, although letting him get away only puts the al-Sadr problem on the back burner again. Better simmering on the back burner than boiling over on the front, for now.
And I shudder to think what might happen if Palestinian militants ever seized control of the Dome of the Rock. That's the best reason to establish a self-sufficient colony on Mars that I know of.