Okay, I'll give you that Tony is nowhere near as cracked as Batman or Sentry. :) And I agree that as things stand, it's obviously a conscious categorization on his part and not a pathology. But I think he does imbue the division with more significance than most superheroes, and I could see how it could become problematic, for the purposes of a fic that's speculating on consequences of the psychological trauma he's endured over the years.

Oh! And there was the fairly recent story about the robots his dad had built, that were basically being controlled by his own subconscious thought-streams. The one where he ended up electrocuting himself to save Cap. I don't think it's the same thing, really, but taken together, I think there's definitely some logic to the idea.

Oh! And the fact that he actually, literally is a combination of multiple versions of himself, if you want to dip back into the canon. He has the memories of his original self (who sacrificed himself fighting Kang), the teenaged Tony from an alternate timeline, and a version of himself who existed for a while in a pocket universe and came about being Iron Man in a whole different way.