Iran couldn't become a 'Great Power' post-1850 without some spectacular PODs. I can see the nation becoming a regional power and gain notoriety in the rest of world perhaps, but power on par with Russia, Germany, France, etc...? It seems far too unlikely to me at least, sorry.
During the 1900s (and late 1800s) the main reason Iran did not modernise was because of the strength of the conservative clerics/tribal leaders. Removing those and other factors that worked against modernisation would be hard. A Meiji Iran would be more easily done with an even earlier POD.