If you use identity-preserve false, you can start the destination SVM (from your SVM-DR solution) and then you can use SnapMirror to vault the individual FlexVol volumes to a tertiary site or take local Snapshot copies of the individual FlexVol volumes in the SVM.
Source =======================>Dest1==================>Dest2
SVM-DR SnapMirror
(-identity preserve false) (vault)
You cannot create a cascade SVM-DR like this:
Source ==============>Dest1============>Dest2
SVM-DR SVM-DR