An interesting question, I think I will brainstorm on it a bit here...
On the neck-thru basses, the neck is critical to the sound and the body wings only play a minor part. The neck wood has been declared to be the key component in your sustain and tone. I suspect, therefore, that any wood inserted between the fretboard and the neck might have an impact on your tone as well. While your concern seems to be aesthetic, I would choose my wood carefully.
Also, the typical ebony board on maple already has great contrast. I would think that you would either have to choose a lighter wood for the board, a darker wood for the sides of the neck, or have multiple laminates to set each other off. Something like mahogany neck sides with a maple veneer between the neck and board might look nice.
Another less intrusive possibility might be that they could route a line down either side of the ebony slab and inlay a strip of a lighter wood. In my vision, this line would basically connect and contain all the position markers. It would give a similar appearance without actually placing a veneer between the slab and the neck proper.
Looks like my train of thought has reached the end of the line. Is there anything here that sounds interesting or helpful?
(Message edited by bsee on May 20, 2004)