Since the POD I presented was unworkable, I'll leave it open. Somehow, Fatimid Caliph Ubayd Allah al-Mahdi Billah is able to successfully invade the Emirate of Cordoba and make it part of the Fatimid Caliphate. This would happen during the 920s. The POD could be anything that would allow this to happen.
So if Al-Andalus was under Ismaili (Shiite) Fatimid rul, what effects would this have? What would a more western-oriented Fatimid state develop like? Might the Ikhshidids of Egypt survive longer? Might the Fatimids not expand into Egypt at all?
On an unrelated note, is the reason these WI's always go unanswered because people on AH.com are not as familiar with the site?