Secularism is needed in Iran.
Historically, secularism has no significant tradition in Iran. Even during the reigns of the various Persian empires, religion played a huge role in our society, and the only difference between now and than is that we changed our religion, from Zoroastrianism to Islam. When Zoroastrianism was still the most dominant religion in Iran, the Magis, Zoroastrian/Mazdaistic priests, had the same role as the mullahs have now. Reza Khan tried to secularize Iran's society, but unlike Ataturk he failed to destroy the mullah-clan in Iran. His plan was doomed to fail, considering the amount of illiterate Iranians back than and the backwardness of Iran's society in those days.
But compared to Iran today, many Iranians are young, literate and well-eduacted. Most Iranians are self-conscious and know what happens around the world. The mullahs tried to stop the flow of information and modernization in Iran, but the complete opposite happened. Iranians are, especially compared to their neighbors, secularistic-minded, democratic-minded and ready for all kinds of reforms. The regime can try to halt these developments, but in the end its inevitable.
Not all mullahs are bad. You have (had) enough mullahs, like Ayatollah Boroujerdi, Montazeri and Shariatmadari, who oppose the idea of the Velayat-e faqih system, and have made clear that the mullahs have destroyed the dignity of religion in Iran. They too support the idea of secularism in Iran. They have made the Iranians more secularistic, anti-Islamic and modern minded. Like Reza Khan achieved the complete opposite with his secularization plan, the mullahs have achieved the complete opposite with their Islamic propagation. The moral of the story? You can try to force a society in a particular direction, but you would only create a blowback.
So this current regime and system could survive a couple of years/decennia more, mostly by using force, but the movement is morally dead and if they don't reform from within, it will come from the outside. You can't try to stop these developments.