Hossein, I appreciate you’re responsiveness!
I didn’t mean to discount your concern, you understand this way better than I do, but:
Apps can’t access other apps’ data, and run without privileges. Right? I suppose a malicious app could delete commonly accessible data (just as non-rooted file managers can do manually), but from a security standpoint, I find it hard to imagine what district difference there is between the issues associated with this functionality, and those associated with any other app given read, write, delete privileges. Malicious app behavior and end user non-comprehension of the implications associated with app requests for access is a generic issue for Andriod (as it has been for Windows).
On the issue of extension incompatibilities and conflicts… see PM.