Politically, Hiraab is basically Hawiye. And Federalism for Hawiye is never going to work, which is why Jowhar, Hobyo, Dhusamareb, Balcad, etc are developing at a snails pace. The capital is all in xamar and it's nearby tuulos. It's of course the smartest thing to do, but has it's drawbacks. Hirshabelle & Galmudug are paper states that were invented just so the MP and senator numbers added up.
If economically, your people are centralists than you can't politically be federalists. That's a retarded thing to do.
Federalism still means a strong central government I'm sure you know this. If Banadir, Lower Shabelle, Hiirshabelle and Galmudug become one single super Hawiye federal state then neither federalism nor centralism will make any difference