Iran not going for nuclear capability at this point is just an extended and elaborate form of national suicide. At this point, I think there's no need for regime change, as regime change would only increase the likelihood of a nuclear Iran.
I don't think going nuclear is going to help Iran much. Israel is also nuclear, but that didn't stop Hamas, Hezbollah, Houthis and Iran from launching missiles. Iran basically caused utter destruction on Israel.
Russia is also Nuclear. That didn't stop Ukraine, a non-nuclear state from launching strikes against its capital, oil facilities, strategic bombers and so on.
India was also Bold enough to hit Pakistan in its Capital and military HQ. Pakistan was bold enough to strike back hard at India in Delhi too. Both Nuclear powers.
So, recent events have shown having Nukes is not a guarantee that you will not be attacked with conventional weapons on the most sensitive of targets.
Iran's issue is preventing Israel and US from attacking Iran and trying to destabilize the government and destroy the country's important facilities. And having nukes is not going to stop that.
But going for Nukes pretty much ensures the entire world will treat Iran as pariah including its biggest supporters such as Russia and China.
I don't think Iran wants to be isolated like North Korea. So, it cannot go for a nuke when the benefit is not there.