Not being a luthier, take my input FWIW --- but I've seen numerous, very fine, basses and guitars with cocobolo fingerboards after Brazilian rosewood became a protected specie.
Matt (FBB Custom, above), Rob Allen, Garz Guitars, Brubaker, READ, Matt Pulcinella, and Bone are all bass luthiers who have made fine looking cocobolo fretboards for electric basses.
Here's a link to a nice pic of coco fretboard made by dhuff, (luthier and TB member), -
I guess the trick is the oils and sealing the wood. The luthier who is making my bass with a Nicaraguan cocobolo body top has had a hell of a time trying to seal and finish it without the oils screwing up his hard work.