No it is not possible to replace the vault disks (first 5 disks in DPE) all at once.  If there is a need to have only NLSAS or SAS disks it should be ordered that way. The Operating Environment is installed at factory and there is no way (or I would say easy way) to just swap the disks.  It is still under discussion with feature teams internally to make this possible in future. If the disks are swapped like that the SPs will go into service mode at next boot and may result in data loss.
Hi  Would it be possible to replace a Vaultpack on a VNXe. So that you change the Vault pack from NL-SAS to SAS disks.
Replace VNXe Vault drives from NL-SAS to SAS