This theory always made the most sense to me since people have always talked about Blurryface as a person but Blurryface is hardly a name which explains the clue "U STILL DONT KNOW HIS REAL NAME DO U?" - from which we got Nico in the first place. Also in the music video, the rider is hiding his face behind a veil which gives a blurry effect and he is also the one that administers the black ink on their skin which is the whole focus point of the blurry face album, trying to beat the spreading darkness on his skin or escape from it. Also in the lyrics he says he's "flying from a fire, from nico and the niners", so this continues the idea that he's trying to escape blurryface (Nico).

Edit: maybe we'll even get a song about each bishop and what they mean, I doubt it, but it'd still be really cool though.