I was right...late, but right. The Gran Chaco seems to be a disputed region between a very small Paraguay and Bolivia. I believe, historically it is seen as Bolivian, though Paraguay had settlements there. Bolivia had little interest in the area (do to its inhospitible nature) until they lost their coastline to Chile...at which time the Paraguay River was now the only means of getting to the Oceans. The final thing that set the two nations off was the spectualtion of oil in the Chaco (in 1928 oddly enough), which it has in minor quanties they discovered later.
I don't know if it is important enough in Wesworld to alter the map to reflect the historical per-war Bolivia and Paraguay, or to assume that the situation with South Africa "forced" Paraguay to take those lands by force earlier in history...or some other such thing that caused the change in territory to what we see at present. I doubt Bolivia and paraguay will have their war this time around since even if Bolivia had the port on the Paraguay River...they still have to get past South African held territory to make it to sea, and with the present South American Alliance system in effect, I doubt Bolivia and South Africa get along. The old speculation might drive a different kind of war, with different players, but I do know that Bolivia still has designs on getting its old coastline back (even today).