Wordpress Plugin for Registered Users and File Sharing

We are looking to expand on the Wordpress plugin that was built for allowing registered users to access files. 1) Current functionality: We can create or name new category for file uploading. 2) Current functionality: We can assign those files to selected registered users. We are looking to add 2 new features to the plugin: A) We would need sub categories under main categories. Should be able to create subcategories under subcategory. So that files can be assigned to sub category. B) Users should be able to see files which they are not currently access to. Grayed out with a lock icon image. That can be clicked to notify us by E-Mail of their interest. Simple explanation: They can see the files but they cannot down load the files. When the click on it, we should receive an e-mail of their interest.