WordPress root directory change + Theme directory change

You can move the installation and also plugin and content folder. The follow source demonstrate this.

//*
// Custom content directory
define( 'WP_CONTENT_DIR',  dirname( __FILE__ ) . '/wp-content' );
define( 'WP_CONTENT_URL',  'http://' . $_SERVER['HTTP_HOST'] . '/wp-content' );
// Custom plugin directory
define( 'WP_PLUGIN_DIR',   dirname( __FILE__ ) . '/wp-plugins' );
define( 'WP_PLUGIN_URL',   'http://' . $_SERVER['HTTP_HOST'] . '/wp-plugins' );
// Custom mu plugin directory
define( 'WPMU_PLUGIN_DIR', dirname( __FILE__ ) . '/wpmu-plugins' );
define( 'WPMU_PLUGIN_URL', 'http://' . $_SERVER['HTTP_HOST'] . '/wpmu-plugins' );
/**/

Source for the code example. https://github.com/bueltge/WordPress-Starter/blob/master/wp-config.php