I think the Persian Shia metaphysician, Mulla Sadra (16th century) is the kind of thinker you're looking for. Mulla Sadra is arguably the most prominent Muslim theologian and philosopher ever for he succeeded in infusing various distinct philosophical traditions (Peripatetic, Neoplatonic, Sufism and Shia esoteric wisdom) to found the school of Transcendent Philosophy (or Theosophy) at the heart of which is the theory of primacy of existence over quiddity.
Based on this core theory all phenomenon are explained in terms of various manifestations of the supreme reality of existence. His other major contribution was the theory of Substantial Motion. Based on these two ingenious innovations he also succeeded in solving many perennial questions of philosophy and theology most notably the religious doctrine of Resurrection and in general different stages of human natural, mental and spiritual becoming.
For studying him, you may want to first have a look at the Wikipedia and Stanford entries for Mulla Sadra, and then access the following two papers that focus on two primary aspects of his philosophy:
The Sadra Foundation is also an Iranian institute dedicated to study and promotion of this last but widely unknown genius of Islamic and world philosophy. The website hosts many scholarly papers. But a little bad news is that some of the site links are faulty and you may not be able to locate some categories.