I don't know... It seems to me that the only notes sounding at the nut end would be the occasional open string. The strings between the nut and the slide are normally damped with the heel of the hand. That technique should prevent string vibration from reaching the nut. If the strings being sounded aren't damped one would expect the note at the nut to be determined by the string length minus the note at the bridge. My guess is that the whole thing would sound dreadful.

If you're interested in strange Dobro-like instruments, a friend of mine, Roger Anderson, builds specalized "resophonic" instruments including Banjos. People are already recording with his instruments. He has made five, ten and nine stringed resophonic banjos with outstanding results.

      - Mark