You say having humans on the opposing side is the only way to produce sufficient challenge to make it interesting? Have you ever tried rock climbing, for instance? Or how about finding a large roadless area (you'd probably have to go to Northern Canada) and hike away from the nearest road for about five days, starting with nothing but three days worth of food and a pack. Be easy on yourself if you like. Wear clothes, take a knife and some cord, maybe some matches. Take all the cameras and film you want. "Unfortunately" it's difficult to commercialize this kind of sport.
So I suppose you also want the audience and the experience of that team spirit (or lack of same). Okay, take some of your friends with you, especially those with a lot of meat on their bones.
You say those "athletes" (more like businessmen) are out there to kill and maim each other voluntarily? Not really. They are slaves to a culture that worships the Almighty Dollar, like most of the rest of us. We aren't forced to work at any specific job. But we are programmed with the idea that the consequences of not working - at something someone else (often unidentifiable) considers useful - are very unpleasant.