MySQL copia un usuario

¿Qué tal insertar en otra tabla, actualizar columnas? Algo como:

CREATE TABLE user_tmp LIKE user;
INSERT INTO user_tmp SELECT * FROM user WHERE host ='localhost' AND USER ='root';
UPDATE user_tmp SET user = 'readonlyuser', Insert_priv = 'N', Update_priv = 'N',
    Delete_priv = 'N', /* TODO: ADAPT TO YOUR SUITS */ LIMIT 1;
INSERT INTO user select * FROM user_tmp;
DROP TABLE user_tmp;