I have somewhat interesting development situation. The client and deployment server are inside a firewall without access to the Subversion server. But the developers are out
You don't provide information on what is allowed through the firewall. I'm not familiar with UnleashIT.
I guess you could have a script that exports from SVN to a folder on the SVN server. The script then zips the exported files. You can then transport the ZIP file however you want and extract to the deployment server.
TortoiseSVN supports proxy servers so you could use one of those from the client's side?