Brazilian here.
Brazil is OK for me. Let's see why:
Brazilwood camp: It's very well represented in the game. It had a strong economical and cultural influence, and it gave the name to the country, so I guess this is very important
Pracinhas: It's OK. The ability in the game represents what happened in Brazil after the WWII. Also, the unity icon is awesome. But I think that the air force had a more important role than the infantary, with the "senta a púa!" squadron.
Carnival: It is inevitable, isn't it? When you talk about Brazil, the first thing that comes in mind is Carnival(maybe Ronaldo). But the UA is too specific towards a culture victory. I know you are supposed to win with a cultural victory with Brazil, but I would like some choices. The UA won't help much at a domination or science victory, IMO.
I don't like the colors either. The combination is cool and smooth, but yellow is a must.
Pedro II is a logical choice. I can't think in other person (maybe Duque de Caxias, but he wasn't a leader).
EDIT:Getúlio Vargas and Juscelino Kubitschek could be possible leaders too, after thinking about the topic. The leaderscreen is pretty good, well conected with his personality. Another option would be the Botanic Garden in Rio de Janeiro, where he used to go often. One thing that I dislike is his voice and some phrases. The voice is too 'young', and some lines are too informal.