As far as I know its not possible. In my experience when using the path finding behavior, you really have to take it into account when designing your game. Its current state is unfortunately very weak, and any concept that requires to much use of this behavior, can vey easily ruin the whole idea, simply because you get these "time stops" every time you have to update the obstacle map.
Think your best solution is to make one yourself, which is probably not easy, or hope that they improve this behavior. Or simply redesign the concept of your project so you don't have to update the obstacles more than once, reduce number of enemies etc.