I had an idea, which would provide monthly rewards for ranked players in the battle frontier.
This idea would reward the players with such as battle points, items that can be achieved in this area, or money.
Depending on the player rankings according to the building in which they are classified, the rewards could be different.
I think it would motivate some players to spend more time over there if their efforts are rewarded.
The rankings could also be reset at the beginning of each month, like that each player will have a new chance to win prizes.