This would make a ban from any realm essentially a guaranteed death sentence. You're going to be desperately avoiding battle with any realm allied with that realm, because you know that as soon as they get you, you'll be handed over to the realm who banned you, and you'll die.
It ruins fun for anyone who has even a single ban on a continent.
Yes, I know, it can be frustrating when there's a character out there that you really, really want to kill, but just can't capture a second time...but BattleMaster deliberately makes it hard to kill characters. Remember, one of these days, that character that someone really, really wants to kill might well be your own.
