Fair enough, but we also know demons can kick start a body again from Wynne.
If it is still the original Cole's body, and the demon!Cole inhabited it, he'd still have the psyche and personality of the original Cole. He'd be no different. Both Anders and Wynne still exhibit their base personality, with Anders slowly warping throughout the game, and Justice shining through multiple times. When Conner was possessed, he was still himself when the demon was not in control. I'd be more inclined to believe it's the original Cole if he ever recollected any memories aside the one traumatizing one we witness in the Fade. The only one he seems to have is the murder, and then rotting in the cell. Of course, lack of information does not mean it doesn't happen but I find it strange personally.
It could have merely been an illusion from his constant blood magic you realize?
Patrick Weekes confirmed in the Cole interview on the DA:I website that he was not using blood magic. He was using demon/spirit magic/powers.
Possible, but i am willing to stick with what we know of their kind and make my guesses from that.
We know very little though, and the people of Thedas know barely anything either.
We possibly have an undead capable of blood magic, a shade or an abomination.
My three theories.
Yes, my main point was that there is evidence against him just being a straight up abomination. I'm not going to try and convince you he's not an evil monster or anything.