Daniel Dae Kim is a really inspired cast choice, however, I'm leaning towards Rick Yune.
I loved him in Die Another Day. He had that whole creepy look to him and edge that could be right for this revamped Mandarin they're going for. Plus that picture of him in the first post just sells it for me.
Someone in this thread asked earlier, how are they going to portray Mandarin and his rings without it coming off as cheesy. I've been contemplated this a little and I think I've come to a somewhat plausible conclusion.
Tony Stark comes back in town, ruining Mandarin's plans to overtake Stark Enterprises. After Iron Man reveals himself to the public by some incredible display of power, Mandarin becomes obsessed with the techonology on the suit. Mandarin learns of Iron Man's true identity and manages to steal designs. Using the technology of the suit to his advantage, Mandarin creates gauntlets that he can wear on his wrist/hands, (Think of Graves in Die Another Day with his weapon armor) capable of emitting a powerful pulsor beam. (No 10 different powers, 10 different rings). Now, aiding by his weapons, Mandarin also has a knowledge of Stark's injury, based on the plans for the chestplate in the designs he stole.