Would it help contain the spread? This started with just a small number of people, and so even a small reintroduction would reset the clock two weeks later.

There are a lot of advantages to spreading it out, by reducing the peak strain on our health care resources and possibly letting a vaccine or drug come about. But a vaccine is likely months off at best, and we can't shut down everything until then. So a two-week quarantine might reduce the death toll, but I'm not sure it will dramatically reduce the number of people infected.