As they construct their full or partial Islamic state, ruled fully or partially by shariah law, perhaps they can borrow from the other functioning Islamic states, such as ....ummmmm ....err... ????
I guess there are Malaysia and Indonesia? Sort of.
A federal state, with partially autonomous states, is the only way Iraq can move forward. Lots and lots of countries are set-up this way and the US was originally constituted this way as well. In many places, it works much better than having a very strong central government.
Sharia law is a horrible code of laws on which to base a country's law and order system. The Iraqis know this as well as anyone so it will NOT be the foundation of the constitution. The people who pushed it originally (never really expecting it to make it in) are just looking for a way to save face now while it gets pulled out.