Personally, I would go for #1 United Islamic Republic/Islamic Union.

However, I wouldn't want a single Iranian-ruled empire encompassing all Shia territories, especially since that would appear strangely colonial and opposed to Imam Khomeini's philosophy. For one, the concept of "ethnic group" and "nationality" is much more rigid than before 2 centuries ago due to European-inspired ethno-nationalism. As a Lebanese (for example's sake), I wouldn't want to be ruled by an Iranian with no connection to me except religion, while in past centuries such rule would have likely been accepted. An Irish 500 years ago wouldn't mind being ruled by a Frenchman as long as there was some form of artificial commonality such as religion, even if everything else (language, culture, history) were different.

What I would like to see is a coalition of Shia polities or republics, based on Khomeinism, and allied with Iran and Iranian foreign policy. Traditionally Sunni majority lands such as Afghanistan should be excluded so as to avoid any unnecessary conflict with our brothers in Islam. This union would be very powerful and would allow Shi'ism to be empowered and allow us to push our interests in the face of the West and its puppets.

If such a union were completely impossible and Iranian rule had to be done, then at the very least I would like at least independence on the surface and a form of localized rule that benefits locals in terms of social work, employment, economically, etc as Hezbollah is doing in Lebanon. Not Iraq-style Iranian puppet rule.