I demonstrated the ability to add widgets via the plugin folder itself in the past. If a plugin followed a similar directory structure as the actual site folder, and automatically integrated anything it finds based on which directory it was in, then there wouldn’t be need to control where everything is installed. It’d always be in plugins/pluginname/… This would make coordinating random plugins easier. As long as it followed the rules.
http://forum.getkirby.com/t/plugins-combine-fields-widgets-methods/358/3?u=luke