Alter Checkout Pane validation

Current module's codebase allows us to modify checkout pane structure.
But it is hard to do that because there is code in commerce_registration_information_checkout_form_validate() that makes almost impossible using custom form structure.

 $mail_is_required = $form['registration_information'][$prodkey][$prodkey . '-reg-' . $i]['anon_mail']['#required'];

  field_attach_form_validate(
            'registration',
            $entity,
            $form['registration_information'][$prodkey][$prodkey . '-reg-' . $i],
            $form_state
          );

Please review my way to resolve this problem
I've added a new config to checkout pane settings, and added drupal_alter() in the end of commerce_registration_information_checkout_form_validate()