It is also completely unnecessary. There are two options. Either the current regime makes a "deal" or it's going to get crippled to the point of irrelevance or removed.
Iran and Iraq are very different. Different culture, people and history. It's also worth remembering Iran is not homogeneous, only 61% of the population are Persians. There are Azeri, there are Kurds and various other ethnic/region minorities.
Iran is extremely vulnerable. It has internal issues, constantly oppressing/suppressing its people. Its economy is in terrible shape. Most of its economic engine can be easily taken out (its main oil terminals). The bulk of its military can be destroyed from the air, it has little defensive or offensive capability. They know it.