well walnut as a neck...
i wanted to build a walnut neck as well. i asked a fellow luthier who build a walnut neck-through bass (4 strings). that wasn't the best idea, the customer returned the bass after half a year. fretboard off, carbon reinforcements, and new freatboard ontop. that was roundabout 3 years ago and since then there were no further complaints.
just some input for you...
greetings