Sound like a problem. The much defined problem is: Everyone who take the frontline region, know they are adding a few more regions away from their heartlands from being threaten. Now what is Sea Travel implemented on EC? There will be total chaos! 
When everyone, even the very game mechanics, is telling you to have small realms and you still refuse to change, well... just punish them harder in terms of game mechanics. I will say until the point of have Slimbar going rogue and infested with 50k monsters so you can learn the lesson once for all.
