As far as I'm concerned - as a Muslim, I think that the topic is very interesting! Qur'an is not just a Holly book, but also a linguistic masterpiece! In addition to the interesting topics/areas mentioned above, you can also tackle the following linguistic issues in Qu'ran:
1-the linguistic miracles: especially the miracles of numbers (e.g. the equal mentioning of opposing concepts: paradise vs. hell; day vs. night; light vs. dark, etc.)
2-Consistency between sounds and their meanings for some words and idioms.
3-Dramatization (esp. in Surat Youssef "Joseph Chapter").
4-The linguistic presentation of the same AYAH (verse) may arise multiple meanings and interpretations;
5-Stylistics issues.
6-Repeating the same idea in many different locations, yielding various meanings.
7-Using the most suitable and accurate words to describe EXACTLY what was intended.
**Please have a look at these interesting resources:
I guess you can even go for cognitive metaphor, but don't forget cognitive metaphor has a shaking root. Therefore, you can change the root of it, some sort of reverse engineering.
There are hundreds of ideas pertaining to the Holy Quran and this all depends on the direction you intend to take-Quranic language, themes, Bibi Ashraf Baghi Bibi Ashraf Baghi events and so on.