So can I quote you on believing that plane crashes are caused by extraterrestrials?

Gold.
A dead Khomeni might mean a far more chaotic Revolution. I know only a little on the events of '79 but I remember reading the military brass had totally lost the will to defend the Shah's regime so I doubt a counter-revolution and follow-up Junta.
You have the Marxist/Left-wing Nationalist movements that might come to dominate but if anything will get the Military to pick up and crack down it's Commies.
A lazy part of my brain is seeing a possible Afghanistan writ large playing out in Iran. The Tudeh come to power in Tehran as a broad revolutionary force. Slowly they crack down and become more doctrinaire in their Marxist-Leninist dogma, angering Islamists and democrats alike. The People's Repulic is formed, bandits take to the hills, Soviet arms roll in, the CIA starts paying visits to certain Islamic student groups etc.
However unlike Afghanistan, Iran has far more going for it to warrant Soviet aid. Its oil refinaries for a start, not to mention the much coveted Indian Ocean access. However its also far larger and alot more likely to get US aid rolling into rebel hands. Will Iran's more urban, secular population aid the regime or encourage more mass, peaceful opposition like in Eastern Europe?
Afghanistan will become a sideshow, meaning almost certainly no Stinger missiles for the Mujahadeen. Iraq will be in a wierd position. Saddam will remain firmly in the US camp. He wont dare invade Iran now meaning no decade long war, meaning no economic drive to seize Kuwait. However the CIA will be keen for their man in Baghdad to act against the Reds next door. Saudi money will flow like a burst dam into rebel Iranian hands.
Would be very interesting to see if the pros of a Red Iran will help prop up the Soviet Union or will the cons only help hurry its fall along?