While it's not a bad thought, and may be something you bring up in Next Steps, don't forget the following reasons why you should not press for this during the case:
1) This is not the focus of the case - We're provided with a breakdown of products. So, go with that! We need to use the information that the client has, rather then spend a lot of time getting information we don't have (this applies to real life as well). There will always be unexplroed areas in a case (you have 30 minutes for a massive topic)...but you need to go where we have information
2) We are limited by our production capacity - We can't produce more! We're at full capacity. So, we don't really have the ability to play around a lot...i.e. find what we produce the best and where we currently sell it best, and optimise!
3) Our goal is (mostly) profit margins - This is something to clarify (i.e. how would we like to tradeoff margins w/ market share where needed), but, generally, a business would like to improve margins (i.e. profit) first. So, again, let's optimise for where we know we make the best margins
4) The S American market isn't good (for two reasons)-
a)Price competition - You say there's intense fragmentation. Isn't that a bad thing for margins? In economics, this is called monopolistic competition, and almost always indicates price competition. This means bad margins.
b) Trade isn't that great between S. American countries - Tarrifs, non-porous borders (have you ever flown between S. American countries? Flights are often more expensive than flying to the US), tough geography (mountains, jungles), poor infrastructure, and a low-income population, all mean we'd probably rather throw our goods on a ship (pretty cheap) and transport it to where people will pay more.