That would give Iran too much of an advantage. Not as much as they currently possess, but still sizable, and the legroom to expand either way.
True, but it might also give impetus to change in Iran. I wouldn’t agree to giving Iran more territory. The “state” lines of Iraq were drawn without thought to tribal and religious loyalties and it might be better to separate the warring parties. Obviously, I’m not a geo-political maven, but simply thinking out loud.