This is basically what is says in the title.
I believe a loyalty system should be created to curb the rapid expansion of larger players.
The way I believe it should work is that each tower has a loyalty rating from 0 to 100 with 100 being full loyalty. The farther away the king is, the lower the loyalty is and if the loyalty reaches a low enough level (think 0, 10, 20, 30%), the tower has a chance to become "independent" and needs to be re-conqured.
Anyway that's about it.