Scripting a Smith Chart would be interesting. I'm still learning JSL so it would be challenging right now, but it would be useful. I'll have to give some thought on how to proceed with scripting or other alternatives.
I am in agreement also, this would be very interesting (tedious) to script and I'm willing to take a stab at this. Is there interest in other electrical engineering plots (Bode, Nyquist, etc )?
Add-in is in the File Exchange.