Depends. Strategically there its little importance for Mecca and Medina. HOWEVER, Psychologically speaking, it would have the impact of a hammer to the collective Balls of most of the Arab World. Heck, you could have the troops doing that being exclusively Lybians and Turkish Troops, but the impact would be out of all proportion for the UAR, the Saudi Crown AND the Egyptians.
The mere sight of the two Holiest Cities of the Islam, under Custody of the Turks with Lybian Aid, even if utterly respecting the religious sites and rules of the Islam, it discredits utterly the claims of Aflaq and others of strength, and shows them as "paper Tigers", uncapable of guarding their beloved sites, AGAIN, after Jerusalem fell years ago.
Aflaq its pretty much FORCED if this happen, to throw men and war machines, all to "Liberate the Holy Cities" to the exclusion of EVERY OTHER STRATEGIC or Tactical War Plan. Regardless of the issues of logistics, tactics, enemy fleets sinking anything in the Persian Gulf and the skies over the region not belonging to the Allies.
Its pretty much a potential Death Trap where the Western Powers and the Roman Alliance can settle to make a bloodbath.
Are there any Hashimites left that could be set back on the throne as Protectors of Mecca and Medina? Otherwise what about the Saud's being brought in as the Official Protectors of the Cities?