It's not possible to use the Nodus client with FTB. FTB is made up of mods, which most of which are installed by extracting them into your minecraft.jar. The nodus client itself is a minecraft.jar, also. So. If you put the nodus client on your FTB client, Most likely your minecraft will just die... xD So, no. It's not do-able. You might be able to find a FTB supported hack out there somewhere, though.
Hope this helped, Homie!