Porsche, dangerous game and plains animals are usually something quite different, sure there may be a leopard or buff in the mix, but for the most part, plains animals are from german shepard size, to elk sized creatures.
In what I read no one was suggesting a .243 for anything that will stomp or chew him up. people were talking about using a .243 for the appropriate sized animals. My uncle who was a missionary in southern Ethiopia, and then in Tanzania, hunted extensively with a .250 savage. He had a .45-70 for bigger things with teeth, but according to him, almost everything else was shot with a .250. Mind you, for them, hunting off the great herds was going to the supermarket, you drove out, shot something smaller and tasty, and drove home. They rarely shot large game animals because refrigeration was limited, and they would shoot what they could have cooked or processed in a day.
Seeing as he has the ability to go back and forth for relatively cheaply, the suggestion of taking the whole experience in steps seems wise. particularly when he has some people who are locals offering to help line him up with farmers and ranchers.