That's the core issue.

Will the governing coalition (a fairly likely result in a parliamentary-style system with that many political factions) govern within the framework of the constitution -- empowering it and institutionalizing it in practice -- or will the governing coalition use their new leverage to persecute political opponents and re-draw that constitution to institutionalize their hold on power at the expense of other factions (and almoist certainly undermine the popular belief in a constitutional system in its nascent stages).

The USA faced this as well in 1789-1804, but did come to believe in itself. I hope Iraq will as well. I suspect AdrianII expects the latter outcome -- and his concern is not unjustified.