I would think that if we’re taking all of the different sports then someone that does the pentathlon would do well. They train in the shooting, fencing, swimming, running and equestrian events. Next I would think a triathlete would do pretty good
I’d still like to know what the rules are, are they going to compete in every last sport and every last event? How much are they going to weigh everything? Some things can be learned pretty easy, maybe not come out on top, while others are best learned young. Most of the track and field events don’t get learned until high school or college. By that time a lot of the gymnasts are almost done.
If I were to ‘build’ someone I’d want to start them young in gymnastics, swimming and equestrian. The gymnastics will cover a lot, especially the more ‘dance’ type events and diving. I’d probably mostly avoid the weight lifting events as I wouldn’t want my athlete to be too bulky.