T. Roosevelt really strikes me as the Charismatic/Imperialistic type...I second your Polk traits. If only there was a "Bombastic" trait for T. Roosevelt, then it would be perfect.
There is no point in having multiple leaders for the same Civ if the traits are the exactly the same as the other leaders...to an extent, it is historical time period representation, but it is also picking the greatest leaders you can find of that culture/people and putting them into the game. You may have a duo like Julius and Augustus, both from a particular time period of Roman history but both considered to be fabulous politicians. And their traits are different, so you do have different gameplay with them. Sometimes, fame plays an important role (ex. Aztec leader), although Firaxis has gotten quite better at excluding popular names that really don't match the civilization or were not that great, or even of the same ethnicity as the people being led (*cough Cleopatra *cough).
@jkp1187: Wow, if the sole criteria for placing leaders in Civ was whether or not you liked the leader, that would be fine. Care to back it up?
I would also suggest you look at something beyond the 20th century for leaders. Hindenburg or Ludendorff would be horrible choices for Germany. King Otto I would be a much better selection to represent Medieval Germany. I would also suggest Barbarossa, but he may fit the HRE better. Franco is not a good choice for Spain--he was just a dictator during WW2. If you could explain why you believe he is so fantastic he deserves a slot in Civ, I'd be willing to consider him. However, from what I can tell, Franco is just another WW2 name that people throw out because the only history they've studied is WW2. For additional Chinese leaders, I have seen the following names listed on this board: Liu Che, Zhao Kuangyin, Tang Taizong, Deng Xiaoping or Wu Zetian. I'll add Sun Yat-Sen to the research group, because I don't recognize the name.