The absence of Israel might do the trick. Have the British not be succesfully lobbied by Zionists to set up a Jewish state, in which case France probably gets the entire Levant as their mandate. In which case post independance the Levant conflict will not be between Jews and Arabs but rather between Christian Arabs and Muslim Arabs, with the former being viewed as Western stooges. In this case you probably have France backing Lebanon in much the same fashion that America presently backs Israel, with significant ethnic cleansing and population transfers just like what happened against Jews in Arab countries and Arabs in Israel OTL.
It's questionable whether the same degree of animosity will exist since the Christians are Arabs rather then Western immigrants like the Jews. But Syria is still going to want to unite the Levant under it's rule, and Arab countries are still going to want a bogeyman so they can distract their populations with Jingoism, so a similar dynamic is not out of the question.
Number 2 seems like the most plausible one. Just have different borders agreed on by the French and viola. It would probebly also be the best case out of all the others, as since mount Lebanon had some autonomy, there will be a tradition of self goverment to draw upon. It was something the other Arabs lacked, and look what happened to the rest of us...
Eh? North African Arabs and the Arabs of the South and South Eastern peninsula had a tradition of self governance. Those areas are not notably better off.
Oh I didn't mean that. In some circles, they're not considered Muslim. In that respect, the Assads had managed to protect the minorities.
Well they're Muslim enough to be President of Syria, a role that is constitutionally limited to Muslims.