See, my issue with the info we supposedly have is that we only have a dubious source of that information in the first place. At least in the movies, there's context and a plot that supports the revelations, but with AHTK, all we have to go on are the words of a fundamentalist foot soldier, which are very likely influenced by skewed doctrine and propaganda. In other words, a character like Norriss is told what to think, he isn't an innovator, conspirator, or visionary. It's painfully obvious by the way he talks - "You'll soon suffer horribly with a hole in your body for every ring of our faith" I don't know about anyone else, but those sound like the words of someone who is very easily manipulated to me, thus I refuse to take them at face value until we get something more conclusive. When Killian says "I'm the Mandarin", I believe it because the film clearly shows how he orchestrated all of the events leading up that point. With Jackson Norriss, it's entirely within the realm of possibility that he's still swinging from some myth that was fabricated by Killian at one level or another.
Sure, it could be a guy, but he's likely another perpetrator himself, because he certainly hasn't been alive since the middle ages (unless he's Asgardian, meaning Iron Man could never hope to be a match for him). The idea that it's some title that has been passed down throughout the generation is plausible, but again, we can't make any solid conclusions because nothing that has happened confirms as much.
Personally, I think this whole thing was as Pearce said - just an excuse to have another go at Trevor Slattery as a character. The funny thing about that is that nobody seems to give a damn about Trevor in his own one shot (or the other interesting things, such as Justin Hammer and Seagate Prison), but rather the idea of another villain lurking in the shadows. I guess he failed in that respect, but I know I thought the short was hilarious, and I still enjoyed IM 3 for what it was. Being brutally honest, I don't expect to ever hear from any sort of Mandarin ever again in the MCU. If the speculation is correct and he is out there somewhere, then everything that has happened up to now doesn't exactly set him up to be a compelling villain for Tony Stark, because for the time being, the people he would be targeting are the perpetrators related to the Ten Rings fiasco. Why on earth would Tony Stark get in the middle of that? He'd be doing him a favor, and more over, for what reason would the 'real Mandarin' have for making an arch-rival out of Tony Stark in that case? They have the same enemy if the speculation is in any way accurate.
I'm not completely averse to the idea, because where there's a will...there's a way, and if a clever premise could be written up then it would of course make for an interesting movie, but right now...I'm just not seeing it.