We certainly need indigenous native tribes of South America in the game, Tupi is a good choice, I always defended its addition or the the Arawak.
But certainly Brazil is far more influential than any one of these tribes, Brazil is a huge geographical area of the continent, almost half the population, almost half of the economy, more gameplay options that any of these tribes would offer, among other reasons. No doubt Brazil is the second best South American civ model in the game, after the Incas.
But there are subjective criteria discussed here, some will prefer native civs South America, others will prefer moderns, I prefer both.
