I've been developing a south american pre-independence setting for my own system, but can be easily converted to BRP. It focuses on the "Virreinato del Río de la Plata" which covers actual Perú, Bolivia, Paraguay, Chile, Argentina, Uruguay and some parts of southern Brazil. The "Virreinato" starts in 1776 and is a very interesting period with a lot of different cultures (conquered/integrated natives, free natives, african-americans, european and all kinds of mixes), political intrigue (a fading spanish colony, independence plots, smuggling), misteries (mostrly related to native, christian-native and pagan traditions), and option for realistic or magical play. The most important native people groups are playable: Tehuelches, Mapuches, Aimaras, Guaraníes, Comechingón and Inka. It would be possible to play in earlier times when it was the "Virreinato del Perú". Pre Columbus times are more difficult because many native cultures were destroyed by christian-spanish conquest and warring/absorption between natives, there is not enough information for a deep and rich native setting except about the Inkas.