|Regime change in Iran should be a major priority of US policy. Given its sizable population and military plus difficult terrain, I don't think a military solution is the best approach. A much better approach is to actively support the reform movement in Iran.
My question is how best to do it? Here is a proposal. Maybe you have better ideas.
1. US should openly and continually state that our goal in Iran is to remove the veto power that the mullahs have over military, police and judiciary. With the very important exception of this mullah veto, Iran has a fairly democratic constitution making a smooth transition to true democracy very possible. This is very different from Iraq, Syria, Saudi Arabia and most other Middle Eastern nations.
2. US should not subordinate denuclearization to supporting the reform movement. The mullah dictators are the real threat. Without them there would be no problem with nuclear weapons. This will piss of the Europeans, but who cares.
3. US should officially state the overthrowing Mossadegh in 1953 was a bad mistake that undermined democratic development in Iran and violated our principles. In addition, it undermined a valuable ally against the Soviet Union and indirectly led to the Iranian revolution in 1979. Bad mistake.
4. US should form an organization of Iranian exiles (call it the Mossadegh institute) who actively aid reformists in Iran via the internet. This group should work with the US government to develop a plan for destabilization, post-revolution stabilization and democratization.
5. US should also consider use of CIA/Special forces operations to destabilize the mullahs, particularly if repression escalates.
6. US should not withdraw the possibility of all-out invasion. Without the threat of war, the mullahs will never take use seriously.