因此，在进行了一些修补之后，我提出了以下解决方案：

if($enable_theme == true):
   register_theme_directory( plugin_dir_path( __FILE__ ) . \'themes\' );
   switch_theme( \'mythemename\'); // my custom template/stylesheet name
else:
   switch_theme( \'default\'); // template/stylesheet name
endif;

//Testing purposes
//$current_theme = wp_get_theme();
//$name = $current_theme->get_stylesheet();
//$path = $current_theme->get_stylesheet_directory();
//echo $name;
//echo $path;

function updateTheme($theme){
        update_option(\'template\', $theme);
        update_option(\'stylesheet\', $theme);
        update_option(\'current_theme\', $theme);
}

add_action( \'setup_theme\', \'change_theme\' );

function change_theme() {
  if($enable_theme == true):
    register_theme_directory( plugin_dir_path( __FILE__ ) . \'themes\' );
    $theme = "mythemename";
  else:
    $theme = "default";
  endif;

        updateTheme($theme);
}