Alternate History Hub on YouTube recently released a new video revolving around the concept of what if the McMahon-Hussein Correspondence had been successful and, after WWI, a single Arab-ruled state, ruled by Hussein bin Ali, Sharif of Mecca, was formed covering the entirety of the Arabian Peninsula. I think his video was very well done, but it got me thinking about a similar question I need to answer for a similar scenario in my first Alternate History timeline. What would happen to the McMahon-Hussein Correspondence and the Arab Revolt if the Central Powers had won WWI?
I have a feeling that the Hejaz region would be unable to separate themselves from the Ottomans initially like they had in OTL. If that is the case, there are a couple questions that can stem from this scenario.
1) Would the Hejaz region be successful in separating themselves from the Ottoman Empire some time after WWI? This could be through various reasons which aren't 100% vital but still worth mentioning.
2) If they are, would they have British backing and/or would they be able to hold themselves against the House of Saud?
3) If they were unable to separate themselves, would the House of Saud be able to rise to power and serve as a uniting force for Arabs in the southern regions of the Ottoman Empire and throughout the Arabian Peninsula?