Custom meta data fields?

I would like to see the ability to add additional meta information to any file that gets uploaded. For example, copyright information, author, caption, producer, etc... This info would then be made available to the process that renders the media asset in the WYSIWYG editor (just like Title and Alt) and to the Text Formatter for media tags.

How could this be achieved? What steps would need to be implemented?

Thanks,

Steve