Well, how about this to start with - the Maronite Christians decisively win
Lebanese Civil War and the Gemayel clan, as leaders of the
Lebanese Phalange and by extension the
Lebanese Front which functioned as an umbrella for the Christian paramilitaries, manages to consolidate power after
Bachir Gemayel, their most competent leader (and also one of their most brutal), avoids assassination in 1982. Gemayel turns Lebanon into a Christian military dictatorship with a paper-thin democratic veneer, pushes the Lebanese people to identify as
latter-day Phoenicians rather than Arabs, and probably makes peace with Israel if given the opportunity to do so during or after the Oslo Accords (if they aren't butterflied away of course).
Meanwhile the Muslim Brotherhood successfully topples Hafez al-Assad in Syria, as well as the Egyptian regime following Anwar Sadat's execution. The United Arab Republic rises again as an 'Islamic Republic of Arabia' (or whatever else you might want to call it), and the Ilkhwan persecutes their Christian population - maybe reintroducing the jizya, to start with. Egyptian & Syrian Christians flee
en masse to Lebanon, where Gemayel welcomes them because he needs people to replace all those Palestinians, other Muslims and Druze he's driven out of the country at gunpoint. The Lebanese confessional model of governance, such as it is, might be adapted into a sort of 'permanent ecumenical council' to give each of the various Christian sects a say in how the country is run, though the Maronites aren't going to quietly give up their dominant stake to the Copts or Syriacs any more than they did with the Armenians IOTL.