Bets

For example, the third party could still add more Hives, and there's no way to check.

For such situations, I suggest using not just one, but preferably three people whom both participants trust, who can review the map and give a general opinion, to see if the balance is more or less equal. And in the case of adding Hives, it will be immediately visible.)
Although, with such a number of people, it would be very expensive :D