An ayatollah is the highest-ranking cleric of Twelver Shi'a Islam. I'm not sure that a "pro-American ayatollah" can actually exist, and in any case, it seems inimical to American interests to install yet another sectarian Islamic dictator.
By contrast, Reza Pahlavi, the son of the deposed Shah, has advocated for transitioning to a secular, democratic republic, but letting the Iranians decide by referendum what kind of government they want. From what I've seen on the news and social media, it doesn't appear to me like they would choose to go back to the Islamic Republic and being ruled by the mullahs. My understanding is that a significant majority of Iranians are in favour of a secular government, and only around a third are actually devout Shi'a. Theoretically, if all the mosques and imams vanished overnight, it would have a more devastating impact on the state than the citizenry.