As for attachments, no intention to use it. I would just provide an "file upload" widget and store the file in the CR with the comment_id as the parent_id. Download would be handled through the content-repository as will delete (though I would have to write that page).
Talking about content-repository. Has anyone successfully used /acs-content-repository/index.vuh for retrieving content files? Looking at it there seems to be a certain lack of functionality available e.g. at file-storage/www/download/index.vuh. But we should have a general method, instead of file-storage download, general comments download, contacts download (you get the picture).