Hmm... you do have a point. The current procedure is based on the PvP rules in the last IBT where an attacker (the player issuing a challenge) had to declare an item to go after from the defender's inventory, and if successful the attacker would loot that item. A couple of clauses making it more risky to issue a challenge had to be added to prevent probable spam from players who had no inventory (and originally, nothing to lose) repeatedly attacking those with items.

On the other hand, as the defender, you could stall and wait to see how the standings unfold. Suppose it's 5 minutes until post payout (the end of the tournament) and you're in a tie for 1st place, with one pending battle from an opponent near the bottom of the standings who has attacked you with that 6. In this case, you would want to accept that challenge because you have that 1/6 chance of winning the tournament outright should you tie.

Furthermore, I'm not sure that there exists a ruleset that would be 100% abuse-proof. I'm not going to say how right now, but I do know of a way that I could easily put challengers/attackers at an equal, if not bigger disadvantage under your proposal.

I'm going to defer to @lordnigel on this one and let him have the final say on this.