Seems to me this is what happened in the Balkans post WWII and was called Yugoslavia, which hung together only as long as Tito was around to keep it together by his personal force of will. Is there an equivalent strong man to do the same in your proposed federation? Are you ready for another Bosnia/Serbia intervention? (Oh gee, I forgot, we already have one going in A-stan now, don't we?)
Also seems to me that the history of British colonial rule in the region would be worth consulting, not to mention the experiences of the various Persian Empires.
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