Someone needs to mind the field and all the players- make certain everything is safe and no one is breaking the rules.

[ Because there will be rules, just so no one gets killed. With this group of competitive personalities it'll be something of a certainty that someone, somehow, will be injured. Having a healer on standby is common sense. ]

You do not even know who he is. You cannot call dibs if you do not know who it is you are claiming.