I would not plan for the occupation of Iran. But there are things we should plan for if Iranians finally revolt against the mullah-run government.
Our interests are too limited for that. We don't want Iran to be a threat to allies in the region. We don't want Iran to threaten oil exports through the region. And we don't want Iran's nuclear assets to escape in the chaos.
If there is a revolution, we should limit our direct involvement. Sure, support people carrying out the revolution. As Syria shows, leaving the situation alone isn't a recipe for letting locals settle the issue without massive bloodshed and destruction. But don't go in to directly participate in the revolution.
A revolution ends the active threat by policy posed by Iran. On the other hand there is the threat of chaos and refugees expanding outward.
We'd need to plan for how to insulate Iraq and Afghanistan from spillover effects.
At worst, we might need to seize islands in the Strait of Hormuz to nullify Iranian threats to oil traffic. Maybe Kharg Island, too. Although that oil export terminal at the northern end of the Gulf would be unable to export oil if the strait is controlled. If this operation is carried out with a strike campaign to knock out Iranian air, naval, and ground assets that could threaten oil traffic, that's more than enough war with Iran for me.
I'm not sure what we do with the nuke issue. We've planned for a US-ROK division capable of going into North Korea to secure nuclear sites--presumably when North Korea is in chaos, otherwise I don't see how it fights its way through the North Korean army--so maybe that planning would be useful for Iran. But I don't know. Could we move in, securing or removing key assets, and leave without too much problem?
Those are things we might be able to do that I'd like to see planned, rather than planning for an occupation as a warning not to do it. Oh, and I reject the idea that we didn't plan for post-Saddam Iraq. We did. Heck, it was in the New York Times. But no plan survives contact with several enemies.
And really, I don't think we remotely have the forces to occupy a country of Iran's size without a major mobilization of our reserves and an expansion of our ground forces on top of that.
It is true that in late 2004 I speculated about how American troops in Iraq might support a revolution in Iran. But that was a matter of exploiting American forces on the ground nearby in Iraq. And I didn't want to stay.
UPDATE: It is a symptom of our social media-created short-attention span times that a lot of people reacted to the title without reading the article to understand that the author wanted to plan for the purpose of showing how hard it would be.