Would the Download module help at all?
This all sounds like it should be an extra module, as the Files job is just to handle Files. Downloads are a very different aspect, but you can use the Files library in PHP to get lists of files and server them up?
So:
Files handles Files. Downloads handle the downloading of "Files"
If the Download module by Authur Guy is not good enough for your needs you should definitely think about building one and selling it on the store.