RAX40 USB port usage?

I have a RAX40 Router and I know that you can install a USB Thumbdrive into it to add remote storage but is it possible to add a Cloud Storage device to it and be able to remotely access it?  I have a Seagate Personal Cloud unit that also has another 8Tb drive attached resulting in 16Tb of cloud/NAS storage.  I am trying to consolidate space and figured if I could connect it to the router my devices could access it even when using VPN, my computers when using VPN will not access my external storage.

Is this possible or what would you recommend using?  I also have in place a Plex Media server and considering purchasing either a Qnap or synology unit to run my Plex and my NAS Cloud storage.