I don't believe the Nerevarine is required to be a particular gender or race. I believe the trials make it clear:
Seven trials: What he puts his hand to, that shall be done. What is left undone, that shall be done.
First Trial: On a certain day to uncertain parents Incarnate moon and star reborn.
Second Trial: Neither blight nor age can harm him. The Curse-of-Flesh before him flies.
Third Trial: In caverns dark Azura's eye sees And makes to shine the moon and star.
Fourth Trial: A stranger's voice unites the Houses.Three Halls call him Hortator.
Fifth Trial: A stranger's hand unites the Velothi. Four Tribes call him Nerevarine.
Sixth Trial: He honors blood of the tribe unmourned. He eats their sin, and is reborn.
Seventh Trial: His mercy frees the cursed false gods,Binds the broken, redeems the mad.
One Destiny: He speaks the law for Veloth's people. He speaks for their land, and names them great.
Whoever fulfills the seven trials is the Nerevarine. I also think that Vivec's backing makes a pretty big difference when it comes to accepting the Nerevarine as Hortator.
I already said this, but I don't believe that the Nerevarine is Indoril Nerevar reborn. I believe the Nerevarine Prophecy is itself a Xanatos Gambit on Azura's part to take down the Tribunal. It just so happens that Morrowind needs the Nerevarine to kill Dagoth Ur, and the Emperor (and Blades) saw the need to end Dagoth Ur before he could escape the Ghostfence. So your character in Morrowind is the culmination of both the Emperor's and Azura's Xanatos gambits, for related, but somewhat different, reasons.
What I mean is, any character you choose to play is the Nerevarine. I don't think any particular race or gender or birthsign or choice of Great House is better or more valid than any other, and I don't expect Bethesda to present a canonical Nerevarine any more than they'd present a canonical Blades agent, Eternal Champion, or Champion of Cyrodiil.