To retake Azerbaijan wouldn't be a foolish idea: the poeple are shia muslims (azeri faith, one of the most progressive muslim religions btw but I'm not an expert myself). You could even get British indirect support when Russia is going red. In which case, Persia (not called "Iran" back then) could be an oil juggernaut after the 1940's. And considering Iran doesn't have a tradition to suppress languages and culture in his country (Farsi must dominate the administration and the culture, but you can speak kurdish or azeri without problem), This enlarged Persia could hold until today. And since Iran always saw oil as a money source to modernize and industrialize (from Mossadegh to the Shah), this could lead to a very developped country.