Which version of DFM? Are you using DFM's older Backup Manager feature, or the newer Protection Manager?
If it wasn't for the fact that you've got an R200, I'd suggest you use Protection Manager's "Space Management" feature. I can automatically migrate a SV secondary volume from one controller to another and update the dataset so that its aware of it.
You could do the following:
1. Relinquish control of the SnapVault jobs from DFM. The SV relationships are still there on the controllers, but DFM isn't controlling their schedule.
2. Use the instructions on how to migrate a SV secondary from one controller to another using SnapMirror:
http://now.netapp.com/NOW/knowledge/docs/ontap/rel734/html/ontap/onlinebk/GUID-C7AA0759-C0EE-4815-9775-7CB415860CF7.html
3. Once you've successfully migrated the volumes, import the SV relationships back into DFM.