How to exclude certain variable from the Feature code?
The hook_features_export_alter would allow you to alter the final array of Component names to be exported, just prior to the rendering of defaults.

This allows feature modules a final say in whether or not certain Components are exported.

However the Components' actual data cannot be altered by this hook, so I'm not sure if that actually helps.

Example:

function hook_features_export_alter(&amp;$export, $module_name) {
  // Example: do not allow the page content type to be exported, ever.
  if (!empty($export['features']['node']['page'])) {
    unset($export['features']['node']['page']);
  }
}