I guess this is the main question, can Iranians pull this off without a civil war? Like we did in BD. Folks like Khamenei looks very strong until the moment they are ousted. I recognize the context is different. But is there any chance good guys in IRGC and Iranian army would refuse to supress the protest at some point if the popular uprising is widespread enough? Like it took thousand dead in BD over several weeks, but then we prevailed.
@Rooxbar
No, as the IRGC itself will be the main target of such protests as it has been in the previous 4 mass protests which happened in 2009, December of 2017, Bloody November of 2019, and the latest "Woman, Life, Freedom" protests of 2022. Iran is run by IRGC through the clergy. Iran is only a theocracy in name only. Most Western and outside observers don't realize this, but Iran is a military dictatorship effectively with some theocratic elements.
As a military dictatorship, it is also effectively a police state: according to this:
https://en.wikipedia.org/wiki/List_of_countries_and_dependencies_by_number_of_police_officers
Iran is top 20 for police per capita, Bangladesh is bottom 20. Furthermore, the data for Iran is from 2012, for Bangladesh from 2018 and also the data for Iran doesn't include paramilitary Basij (up to 4 million active members) which act like freewheeling vigilante during protests and are given weapons to use as a grey area force who cannot as easily be tracked and prosecuted.
Iran is also no. 2 in the number of capital punishments, many of which are used against political prisoners (this is also why it's hilarious when people in countries with no rule of law think capital punishment will solve their problems instead of doing a simple induction from how laws are currently implemented to arrive at a picture of how capital punishment may be implemented hypothetically). During the 2022 protests tens of protestors who used violence (e.g. trampled a Basij force and killed him) were hanged. The number of detainees was upwards of 60k, 22k of which were freed with a general pardon a year later when the protests died out.
Iran was also effectively not a modern state in the most important sense of that term until American sanctions deprived them of their free money, aka oil and gas. Until then, effective tax rate was close to 0%, as the government could just coast on the free money. Since then Iran has started a massive campaign of taxation, and hence is not reliant upon fickle oil money to bankroll its security forces.
All of these puts them on strong footing when it comes to crushing any mass movement. However, I'd be much more confident in this prognosis if I didn't know what the people think of the regime. The regime has around 15-20% supporters, most beneficiaries with no real ideological loyalty. Casting aside the 15% apolitical crowd, and 10-15% confused crowd (which although mostly are against the regime, their opposition is not reliable), you are left with 50-60% of the population who hate the regime's guts in varying degrees. Majority of the bourgeois, upper-middle-class higher educated urbanites are in this group and as such have disproportional presence in online places and among the immigrants and diaspora. So if you ask them, they are 90% of the population not 50-60%.
So this level of discontent is not sustainable; either the regime will completely metamorphose after the current Supreme Leader's death or slowly but surely disintegrate from inside. But this, I don't think, will be through any explosive protests any time soon. The IRGC helped Assad bring his planes, tanks and missiles to the playground. In the past 4 mass protests, they haven't even had to resort to 5% of that and they were much weaker back then without steady tax money supporting their security forces.
EDIT: also civil war, outside of very limited engagements in Kurdistan and Baluchistan regions are out of the question, as urbanization rates in Iran are through the roof and no vestige of tribal formation exists outside the regions I mentioned.