USSR fell without much in terms of fighting. The coup tried to roll out tanks but it definitely didn't work

Plenty of guns in Iran's neighbors and in countries with an interest in seeing the regime fall. The US, Israel, Saudis, Turkey, Pakistan, and the Saudis are all big powers in the region who prefer Iran be kept under wraps, without nuclear weapons. Any one of which has the resources to supply an uprising if one materializes.

Not saying a bloody uprising is a good thing, either on the world stage or Iranians. There is no gaurantee the next regime is much better, and you could even see ISIS enter the power vacuum like they have in Iran's neighbors. Granted Iran is Shia so they'd have a tougher road, but Iraq is mostly Shia too and I'm pretty sure ISIS claimed responsibility for an attack in Iran recently...

And without a 'rival' Iran, the Saudis might get even more emboldened. And they're pretty big dicks already

Would be cool if basic human rights were available though. Be a Muslim republic if you want, but hijabs should be seen as what they are..a damn fashion choice.