WI: Israel flat-out invades Lebanon in 1981?

I'm posting this since it has come up in a Cold War forum game I'm running.

What if Israel "flat-out" invades Lebanon in 1981? More specifically (since this is what the player aims for), Israel would seek to overthrow the government at Beirut, install the Maronites, and seek to force the Muslim populations of the country into Syrian-held areas and into Syria itself.

Now I'd imagine this would cause a war with Syria, vows across the Arab world to support the Lebanese Muslims (although I don't think Egypt would actually offer to fight Israel; not sure what Jordan would do), and the war itself would require far more troops than what Israel did IRL a year later, and become domestically unpopular.
 
Isn't this essentially what Israel tried to do in 1982?

Well, except for the part of forcing the Muslim populations into Syria, and that is not realistic. The Sunni and Shi'ite populations are around half of the country, and Israel cannot occupy all of Lebanon. But I assume you really mean the southern region of Lebanon only. Furthermore, it is not really feasible for Israel to expel so many people - it would be a PR nightmare. Also, it would lead to the US clamping down hard on Israel. The US would be fine with Israel destroying the PLO; but expelling Lebanese citizens from their own country is very different. Even if the people who actually did the expulsion were the Lebanese Forces (Maronites), it would still reflect on Israel. It would disrupt the American-Israeli relationship and perhaps even lead to a cut in foreign aid. I don't see this being tolerated. If it somehow was done, then I'd see some kind of Soviet response. There may not be another Arab-Israeli War, but there is going to be some kind of international crisis. Whatever benefits Israel gets, it is probably not worth the cost.

Also, Bachir Gemayel and the Lebanese Forces had to be very careful in their dealings with Israel. While Israel supported the Lebanese Forces, they still had to appear as if they were independent and not a puppet of Israel. If Gemayel was ever going to reunite the country, he needed to be given enough space to make his own decisions. If the Israels downright "installed" the Maronites in power, they'd lack legitimacy.

I don't know why invading one year earlier would lead to any different result than OTL's invasion. And the rest of the POD aren't really viable. I understand that since this is a forum game, that other rules are involved than real life so

Probably a more successful ploy by the Israelis would be to be like OTL except that Israel understands Gemayel's position better and not pressure him to sign an immediate peace treaty, and to leave Lebanon as quickly as possible. A third point would be that the US does not assist the PLO leaving for Tunisia, and that the IDF destroys the PLO leadership in Beirut. Then hopefully if Gemayel is not assassinated, then joint operation between the Lebanese Forces and the IDF drives Syria out of Lebanon (with the IDF then leaving). Afterwards, Lebanon does not conclude a de jure peace, but continues to cooperate with Israel and later after the Cold War ends, Lebanon signs a peace agreement around the same time Jordan does.
 
It would seem that the logistics to expel Sunni and Shia would be beyond the capabilities of the IDF even if it for some reason wanted to do it.
 
One other thing about all this is: what would happen in Egypt, Jordan, Turkey, and other pro-US (and, relatively, "pro-Israel") states? Like I'd imagine Sadat's entire foreign policy would be in tatters. I'd also imagine there would be a sharp spike in anti-government activities in Jordan and Turkey, as well as general ferment in the Gulf. Libya and Syria would probably gain a lot diplomatically, the former for its hardline position against Israel, the latter for being seen as the Arab state holding the line against Israel's expansion.
 
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