If your server environment does not have ArcGIS Desktop, you cannot create a valid file to import.
Not true: You can use the Python within ArcGIS Server to create connection files, via arcpy.CreateDatabaseConnection_management()
The lack of a trusted bridge, however, should prevent any access, so this is really a non sequitur. The publishing process uses the hostname and connection properties from the local machine's connection to the server to identify the registered connection on the server. No identical registered connection, no service.
Therefore, you need a mechanism to publish from a trusted host (via RDP or SSH, or possibly both)
- V