That would be a bad idea if either Brazil or Argentina gets upset in the pool phase, they will have to meet in the semifinals then one of them is going to play in the bronze medal match and will never qualify to the world championship.
It wouldn't be bad if thet have 3 slots but South America only has 2.
Well, just make the tournament a round-robin then. Anyway, Brazil or Argentina can't possibly lose to the other teams. Not even Venezuela is competitive anymore after many retirements, economic crash and the death of Kervin Piñerua.