I have a keen interest in this, but unfortunately i don't know enough of Iran inner workings at the time to guess who could lead for instance. Maybe the Shah's son or the PM will take over? But whatever new government comes will Iran still be in the US camp, or perhaps they will switch to USSR? That would be very interesting, especially on things like Afghanistan.
Are there any other islamist figures that could replace Khomeini, or would the islamist movement dies a slow death, so you have some kind of dictatorship still, but not islamist? If so, the Iran-Iraq war, if it still happens, will be rather different, as in perhaps there will be a ceasefire much earlier, in 1981 or 1982. With a more intact iranian military, the iraqis will be pushed back earlier, maybe even lose some land in the ceasefire.