I imagine with nukes they'd be much like Russia, or Pakistan, or India, or China. In other words, showing restraint and intelligence, and having a deterrent against wars of aggression from the world's highest-funded army.
It's game theory. You start developing nukes and risk US bombing you to stone age while killing your personally. But the moment you develop nukes, US will likely leave you alone. Choices.
US will kill more people through secondary effects of their aggression against Iran, than Iran's nuke ever would directly. True barbarians, except I understand English, so they sound to me less like bar bar bar, and more like a*holes. My gf tries to convince me US americans just don't care and are more like a bear in a porcelain shop. But dunno, I look at Cuba, Iran, Israel and lot of other places americans are very aggressive in/against and it's more like a*holes at this point to me. Whole porcelain shop is suffering. This just isn't the "we are big and stumbled a bit and broke stuff", anymore.
I don't think they should be experiencing regret. The power in nukes is not in using them, it's in the threat of using them. The threat of using them keeps you from being attacked, but once you actually use them, so will the other guys.
This war has pulled the tarp off of their control over the Strait of Hormuz though. That's a strategic weapon they can use without getting nuked back. Iran is much stronger than they were before the war; this was their Trinity test.
And what's truly ironic and moronic, is that the deal the talks are seeking a graceful exit for now would basically be a version of the JCPOA that was withdrawn for pretty much no reason in 2018. Which, if you are Iran, there is zero chance you're going to agree to anything like that anymore now they have all the leverage.