The Mercedes S-class is their biggest sedan. Visit any NFL training camp today and I bet-the-ranch guarantee you'll find several S-class owners who weigh a hell of a lot more than 350 pounds. They don't list a gross vehicle weight limit but I'd double my first bet that it is at least 1000 pounds of passengers and cargo.
The only part that should be affected by a large driver is the seat. Maybe this owner kept burning out the power seat motors, or the lumbar support air bladders, but this is a $80,000 car. Fix the damn seat.