The combo of a Maple fretboard over just about any exotic wood is a no-go. Broadly speaking, the fretboard should be the stiffer/denser wood for best stability. Also, Maple needs a finish and it'd be--to put it mildly--awkward to apply a satisfactory one on just a fretboard.
Walnut shaft + Maple fretboard necks have been done from time to time--but you must finish the entire neck.