To answer you initial questions direct attached 2-way storage is not supported in VNXe.  The 2-way support is being considered for a future release.  3-way is the only option at this point.
Has anyone attempted any type of SAN Direct Access backups for the VNXe?  I have yet to test, but we are currently evaluating VEEAM.  We are getting good results with the proxy appliance method, very similar to VMWare's VDR.  However can I add the VMFS volumes as an iSCSI Volume to a Windows Server, provided I give READ-ONLY Access.  Then the backup sofware will read the VMSnapshots directly from the windows host, rather than the ESXi host.  Currious if anyone has already tried or if its just not supported.
Direct Attached Backups