AH challenge - with as late a PoD as possible, and containing the effects as much as possible to the Levant, have the French army still operating in Syria in '48 and '49.
In OTL, unlike in other French imperial possessions, the other powers really were keen to recognize Syrian sovereignty and get the French out of their Syrian mandate. Meanwhile, the French overstayed the Syrian's welcome and even the rest of the world's welcome, keeping their army around trying to salvage some special concessions from independent Syria. First off, I wonder why even the British in particular, were so interesting in easing the French out there, when they were happy to ease them back in to Indochina?
Anywhoo, if we can keep the French army in Syria, we can prevent the participation of the Syrian army in the Israeli war of independence. Syria only occupied a really small piece of land, but later in history it proved troublesome, and during the war itself, the potential threat of Syria surely had to effect Israeli operations. How does the Israeli war of independence go differently if they do not have to worry about the Lebanese and Syrian armies and are only attacked through Egypt and Jordan by those countries' armies and the Iraqis?
Would the French, if still occupying Syria and Lebanon, also prevent the passage of major guerrilla bands into the Galilee? And would they control the border to prevent the northward flow of Palestinian refugees?
If all the above happen, northern Israel could have a much bigger Arab population (I think only a small number of Galileean Palestinians would pass through Israeli lines to Jordanian controlled territory, most would go north or go nowhere). Would Ben-Gurion, looking at the demographics, actually want to perhaps leave an independent "Galilee wedge" or "Nazarene Strip" in the north, to ensure a Jewish majority, if it can find somebody local to enforce an armistice (hmm, French peacekeepers?)