Iran is a wholly different animal than Iraq or Afghanistan. For one, it has about 3.75 times the surface area of Iraq and over twice the population. And unlike Saddam Hussein's military, which had already been decimated from the Gulf War, Iran has a much more capable military. The other problem is that it would be very difficult to place troops in the areas needed in order to invade Iran. None of the countries bordering Iran, with maybe the exception of Afghanistan or Azerbaijan, would allow the U.S. to set up an invasion force. And getting forces to Afghanistan or Azerbaijan would require going through some tough areas, such as the straits between the Mediterranean Sea and the Black Sea that are controlled by Turkey, or through Pakistan. Iran has a lot more support around the world then Iraq had, especially from China and Russia, who see Iran as a check on Western power in the area. And they also might see a U.S. invasion as a national security threat considering that Iran supplies a sizeable amount of oil and natural gas to them, or at least to China.
You seem to concentrate on conventional war "solutions", which I think are unlikely scenarios. IMO, "war" in Iran would be like dropping a bomb to kill a roach. The more likely solution, IMO, is a return to what has worked in the past http://en.wikipedia.org/wiki/Mohammad_Mosaddegh , http://romneymanassa.wordpress.com/2011/08/19/blowback-the-coup-of-mohammad-mosaddegh/ , using the CIA’s plan http://web.payk.net/politics/cia-docs/published/one-main/main.html . IMO, the past elections have shown the Persian people wanting to be free of the religious rulers.
The Persians I know seem to be very Nationalist and want relations with the West, but without the old controls the US had. Back in the 70s, the Persians I knew were here because the Shah paid them to get an education in the US. My friends seemed to all have the same general deal; education paid, travel to and from home paid (cost them $100/trip, which they got back if they returned), and the only “string” attached was that they come home afterwards and help Iran. IMO, these are educated people, they don’t want their country bombed out like Iraq and Afghanistan, but they do want to have a free country like before the 1979 revolution. Most of my Persian friends don’t give a rip about a Palestinian state, they grew up in Iran around peacefully practicing Christians and Jews, and in my experience, are generally very peaceful friendly people.