I think a snatch & grab in Iran would be a lot harder than in Venzuela.
There are a lot more disafected sources in the later, Tehran is a lot further from the coast or any allied location and the Iranians are used to being bombed and so are better prepared.
Plus removing Kamenei wouldn't solve anything - they have a lot of people looking at that job as it is - removing him would bring in someone younger, brighter and more active.