[quote=@Bartimaeus]
They dont have to be willing if it is forced upon them by the opponent. Someone not willing to fight a child is probably semi-forced into the fight by their likely devilish opponent.
[/quote]

Yeah, but that isn't how the Arena works in general, every fight is pre-arranged and if you want an 'actual fight' then it will have to be agreed. An example of where this would fail is my character Fury in the recent multiverse, where a persistent story forced him into conflict with a number of opponents. He just flew away from a couple of them, refusing to fight because they weren't worth his time. 

In tournament settings this may work, though you would have to get through the vetting process of the host themselves.