It is an interesting concept, however rather than pulling a fretboard off and installing a new one, it may be better to create a neck from scratch.
However, that said, I have a couple of reservations of the idea of using Elforyn as a fretboard material. If Elforyn resembles the properties of ivory it may not be suitable to fret into as it may not compress around the fret tang, meaning the frets would have to be glued with epoxy, probably. Also, as the neck wood will move slightly with the seasons etc, the elforyn as it probably will stay rigid most likely will mean it may be difficult to make the neck playable via a truss rod. The only way to know for certain would be prototyping but I suspect this will be the case.
Another possibility would be to use ebony or an ebony substitute for the fretboard and Elforyn for the inlays and possibly as binding for the neck.
Elforyn is worth looking at for sure as a nut material.