I agree sometimes it's a real trouble, but If people can't be able to follow the rules of their kingdom or can't respect each other , this has nothing to do with the construction of the game.
In my opinion leaders and players have to solve "internal wars" as an internal issue, that's why Travian is a strategical game.
On the other hand an "internal competition" between the players is not so bad in case it's based on the kingdom's rules..
i don't know how it can be done but i was wondering :
if both kings could have access to the camp's rally point watching the process of cleaning the camps...then what?
The problem is you cant evaluate the camps properly as royalty. No clue how you can evaluate camps who already have been cleared. Using hero would be the best solution and - imo - not hard to implement.. I mean the code should be somewhere in the game.. you can also only pick up treasuries from treasury's with hero..