I heard that Sufi icon Jalaluddin Rumi initially wanted to be a cleric, but upon meeting his future BFF Shams Tabrizi, his thinking and understanding of this world completely changed. I would say he become more of a Deist/Agnostic who shunned religious chauvinism and talked more about love and harmony.
Also, the great Urdu poet Mirza Ghalib's eloquently dissed the clergy and talked about his disgust at religious belligerence and hypocrisy.
" The object of my worship lies beyond perception's reach;
For men who see, the Ka'aba is a compass, nothing more."
Though I dont know if we can consider his "unorthrodox" views as being those of an ex-muslim
Yes I would say add Rumi and others...
There was also a group of "heretics" called the Ikhwanu-Safaa' who wrote scientific treaties.
There are others too - I meant to do a search, but got busy - will do in a bit.
But I think you should include all those who could come under the "Freethinker" banner.