Remember you will have to do a lot of messing around with a range of the standard Kobo release including the udev rules and scripts that are invoked when a device is plugged in.
In many ways a far easier approach would be a portable access point that would connect to the Ethernet and provide WiFi access to the Kobo.
See
http://www.asus.com/Networking/WL330gE/ or
http://www.dlink.com/ca/en/home-solu...d-access-point for examples of devices that provide this functionality.