The concept of a Battle Field Event is truly an exceptional idea. With a few minor improvements, it will bring alot of life into the game. It occurred to me is that there is a fair degree of cooperation among most empires. This is good yet at the same time it removes some of the challenge (and hence fun) from the game. We need challenges to keep things exciting. Please read my suggestion for the Battle Field Event.
I propose taking the concept one step farther. Create a PvP Arena Event. Players could get a packet of entry tokens to enter the PvP Arena. Inside would be a free-for-all where players could join up and team together or could fight solo. As a player remains in the Arena his or her win % increases. When one player reaches 100% the battle is over. Killing opponents in the arena would boost win % slightly as well. Depending on the honor of the player killed the win% would go up more the higher the honor.
The score board would display the top 5 players leading in win%. The top 3 would get a random King Certificate, gold coins, and chance at permanent fashion. Other players would receive a PvP Arena Reward Chest similar to Scroll of Chance with some additional chances such as King Certificates.