If you can catch the hive just as the cells are started, you can remove the queen and harvest the cells when they ripen but before they hatch.
Good catch Lee. That was my concern. I have yet to find a specific ETS Estimated time of swarm. Usually, they swarm three or four days before the queens emerge, sometimes as much as a week, and in a nuc I think the problem is compounded.
Like Lee said, if you can pay close attention and get the original queen out of the nuc shortly after the cells are started, it would be a viable plan.