After encountering this error message: elFinder library was not found. Please download it from http://sourceforge.net/projects/elfinder/files/ and install to . (Currently using elFinder Not found) and having had to futz with the placement of various external files to get things like the WYSIWYG plugin and PLUPLOAD plugin working, I had an idea.
Here's the idea. Drupal requires PHP Curl already. It already handles file uploads. If a plugin needs an external library, why not have curl fetch it? If curl can't fetch it (i.e. SourceForge and their bogus mirrors), give the user a field to upload it. The developer of the plug in knows which bits of it need to go where, so just let them deal with it instead of making a user poke around their file system randomly guessing where things might need to be.