Lol, it's pretty much the same stuff I've been saying this whole time
Battles could go on within Tony's mind after it gets hacked/hypnotized by Ultron/Mandarin...That's how they'd balance characters, if Stark is kinda like Hawkeye in this one. Most of the movie he'd be fighting himself/real Mandarin tho. He wouldn't be made to fight the team like Hawkeye was. Rhodey and Banner would protect him/help save his mind (Banner would have to be that kind of doctor and help de-program him from the mind control (same techniques used on Bucky, BW helps). Trapped within himself, instead of trapped in the suit. Banner knows what it's like to have to share his personality with another alter ego, there's this other part of his mind called the big guy.
It would be all about the psyche of some of the characters, i.e. Tony Stark and Banner. It's been as much about psychological/character growth this whole time as it's been about becoming more of a hero. The movies are kinda like character studies some have said, we are supposed to look deeper into their psyches..The suit is now a part of Iron Man's psyche, he joined it to his mind, his subconscious activated it in his sleep. In AoU it protects him on the inside instead of attacking him in his sleep, because of his progress in balancing his alter ego, can defend him in Inception like battles on the inside. It comes out of him instantly in innerspace, where he gets the ideas for the shapeshifting nano tech suit for the outer world. Killian said he was the Mandarin in an egotistic way. It's like when Stark took credit for the suit in IM1, when he said "I am Iron Man", enjoying being known. Killian got tired of being unknown...sick of false faces, he wanted to take responsibility for his creation -- although Trevor "brought the character to life". In IM3, Stark says it again, in a new and different way. Killian egotistically took credit for the Mandarin, he's at the start of his character arc, it's not "a part of him" yet. Not part of his psyche completely. When Killian says "I am the Mandarin, it was me all along", it's like an arrogant/egotistic Tony in IM1. Tony's egotism is on full display in the beginning of IM3, when he says he's the best... It's hard to re-grow a head, because you need to regrow the brain and the mind, so if Killian's brain gets damaged he has to have his memories on backup to be inserted into the re-grown head...The dragon symbol is already a part of Killian's subconsciousness and his body, he doesn't know it's working through him and connected to the entire universe.
I really do think we'll see "Trevor" again very shortly, as well as the Captain America-looking tattoo that was on him in the early trailers for IM3. Things that didn't make the "final cut" of Tony's story. If Tony's mind had been allowed to see the tattoo inside the story he would suspect Trevor more.
Killian may have written the speeches + controlled where cameras were placed and the final edits etc... but wasn't the one who acted it out the right ways to make the Mandarin idea seem real to the world.
In the comics, Fin Fang Foom created Mandarin and at times controlled his mind, he may feel he is Mandarin at this point. Killian/Foom "accidentally" showed us the map of the universe because it's trying to get home and its energy is trapped in Killian's body/mind right now. It knows that certain brains, and especially those of Celestials, are connected to all of space-time, and has been hiding in the back of Killian's mind waiting for a way out, after sleeping through the ages in Alexander the Great's bloodline/genetic memory. Killian called himself "Killian the Great" twice to Pepper, this would be because he's related to Alexander the Great and not Genghis Khan. The villains programmed "the Master" persona/codename into Trevor, Falcon is "snap" and Tony's new alter ego has been created as "The Mechanic", someone else is the Clairvoyant. Winter Soldier's mind has been programmed in some way that's hard for Widow to deprogram. The scepter in IM1 wouldn't work on Tony or the man in Germany, human minds are too "unruly", the villains needed stronger forms of mind control that affect memory and personality. A simple knock to the head brought Hawkeye out of it, this would be far more subtle and invasive tech/hypnotism secretly affecting memory and personality.