Hmm, I too am tempted to add Bolivar to my Venezuela mod but I'm not sure "WHAT" can happen!
As for your question...yes MadmanOfALeader, I tried and it is possible...
I was trying to do something very similar, although with the King of Spain. For some reason, everything works...except for the eyebrows. I have bright pink lines over his eyes. I tried the same with Logan of the Iroquois as another Native leader and Civ, and I have the same problem. How did you avoid the graphics bugs?
I thought it had something to do with the lack of a noshader .nif file, but I'm not a graphics expert (I have done no graphics editing on my own). I tried substituting the base leaderhead's noshader *.nif file (for the King of Spain, it looks like Qin Shi Huang)...but that didn't work.
Or, what did you do to add him successfully? I've never added a Civ, so I'm making it up as I go along. I tried to upload the Native archers from the game (the Braves), and all I have is an archer who looks like he has been crucified (not animated at all).