I mean, if someone has the hardware & software in their own home, there's really no telling what they're going to do with it. Maybe they're just mod the Game:ref to say you're not cheating when you are. Or some other method of circumvention.
The only game competition that I would trust is one where they all played on identical equipment on a controlled network in an room ('arena' seems too lofty for 'place to play computer games'). If money was involved, (10's of thousands or more) I don't think it's unreasonable to request everyone show up in a common location.