Pull callbacks from a hook as opposed to allowing users to specify a function name through a textfield

The "Rewrite Items via callback function" filter allows site builders to specify a function via a textfield that alters the facet items. Ideally the callbacks should be defined in hooks so they are whitelisted which would prevent arbitrary functions from being invoked. To outline the idea, a hook could be named something like the following...

/**
 * Implements hook_facetapi_rewrite_filter_callbacks().
 */
function mymodule_facetapi_rewrite_filter_callbacks() {
  return array(
    'mycallback' => array(
      'callback' => 'mymodule_rewrite_callback',
      'label' => t("My module's Facet API filter rewrite callback."),
    ),
  );
}

/**
 * My module's Facet API filter rewrite callback.
 */
function mymodule_rewrite_callback(&$build, $widget) {
  // Do stuff here ...
}

Then you could use module_invoke_all() to build a form element where site builders could toggle which functions are invoked. That way it would be whitelisted which would add a layer of security and prevent unintended errors by typing in a wrong function name.