Recent versions of FreeBSD have gotten zfsd(8) for this exact purpose. It will automatically enable hot-spares and do some fault resolving. I would expect it to complain loudly if any of the existing pools become degraded. It doesn't seem to have been backported to 10.x though, but 11.1 should have it.One important think I noticed, there is not any sort of obvious notification that the disk was missing.
Recent versions of FreeBSD have gotten zfsd(8) for this exact purpose. It doesn't seem to have been backported to 10.x though, but 11.1 should have it.