You know what would be awesome?
We have 2 versions of Nidoran based on gender, who evolve into separate pokemon.
We have region based shellos.
Chess always has 2 sides, a white side, and a black side, and we have Pawniard, based off the black pawn. It would be cool if X and Y introduced the white pawn. This white pawn evolves into the white knight, and evolves into the king, while bisharp evolves into the queen. I couldn't figure out a cool pokemon design for the rook, but it worked well for digimon (see Rookchessmon).
This white pawn will still be called pawniard, but will be part steel part psychic, or whatever type that is supposed to represent good, as Dark means evil.
Not only Pawniard, but other pokemon can have 2 different versions based on some geographical, gender, or some other barrier, to give it diversity, if you know what I mean.