I think this is one of the key differentiators between Lab Manager and vCloud Director. In ESX Classic, we had the smbmount command. Lab Manager's export feature mounted the CIFS/SMB share directly to the ESX Classic host.
vCloud Director, as of 5.1, doesn't support any ESXi os which supports local CIFS/SMB mounts. It just doesn't exist anymore in ESXi (all versions of ESXi, including 4.x and prior).
You have to use the upload/download feature to go to a UNC path, which will route through your local browser/OS then to the share.
Maybe you can create a VM that acts like a "transfer system" that has everything setup and tested, and may exist rather close to the vCloud Director cells. that way you could just login to that box and perform the transfers.