Well, you can use vfiler-DR for migrations, altough its primary use case is DR, but you won't get any guaranteed cut-over times.
DM-for-vfiler is designed for migrations only and does not work for DR. In order to cut-over the services both vfilers need to be alive so that the DFM server can talk to them coordinating the cut-over.
Cut-over will not work if either vfiler is unavailable, which for DR would be the case.
regards, Niels