Request noted. Here's my input before locking the thread.
One problem with abalone, and obviously metal inlays is they are difficult to work with. So if you had a metal (or even more 3-d screw inlay which i think would be cool) you would have to cover them in plastic or counter sink them below the fretboard. This is because they must be sanded to match the curve of the fretboard.
When creataing a neck, inlays are glued in the fretboard. Then the entire fretboard w/ inlays is then sanded to match the curve (radius) of
fretboard radius. If this is not done, the inlays woyuld be palpable to touch. When the fretboard is silky smooth, the frets are typically installed, then dressed.
Ultimately this allows the inlays to match the radius (curve) of the fretboard exactly. Many good ideas are not quite possible given current technology and machinery... glen