WooCommerce Customer/Order XML Export Suite - change root element of XML document.

wc_functions.php

// Change first letter of XML tag <Orders> to lowercase.
function custom_xml_root_element( $export_type ) {
	return lcfirst( $export_type );
}
add_filter( 'wc_customer_order_xml_export_suite_xml_root_element', 'custom_xml_root_element', 10, 1 );

// Change <Order> tage name.
function custom_order_format_tag_name( $orders_format, $orders ) {
	$orders_format = array(
		'order' => $orders,
	);
	return $orders_format;
}
add_filter( 'wc_customer_order_xml_export_suite_orders_xml_data', 'custom_order_format_tag_name', 10, 2 );