Not doing this as an Islamophobe, but I am very interested in the possibility of widescale religious conversion after 1600. With Christianity, the world's biggest faith, it is largely our timeline, with the Enlightenment eventually causing widespread secularism and agnosticism by the 21st Century.
But what about with Islam? Secularism seems to have far less impact on the Muslim world, so conversion to other religions seems to be more hopeful. Bonus points if you get any of the following areas to majority convert to other religions:
- Indonesia
- Muslim parts of Indian subcontinent
- Egypt
- Iran
- Turkey