Append filename or change upload folder

Hi,

This plugin works great, just what I was looking for and should be in the core.

However, I’m trying to hide files from non-logged-in users by using this trick; https://anchor.host/2016/09/13/protecting-static-files-with-php-script-and-wp-engine/
Which also works great, but it does so either for all files or files with a specific element (i.e. appendix) in the filename.

So my question is; am I able to choose an upload location for the attachments (so I can change my redirect rule), or automatically append the filenames of attachments? That way, I can set up the correct rule to hide these from the public.
I realise this might be pushing the plugin a bit, but it would be awesome if I could achieve this somehow.

Thanks a lot!