I suppose you could try to use the "If the only reason your doing something is game mechanics, you're probably doing it wrong" philosophy with this. If the only reason you're forming your "it's-not-a-religion" religion is to keep real religion from coming into your realm, then the only reason you're doing it is game mechanics.
Perhaps some parallel could be drawn to declaring war on another realm, and then sending message saying "We're not really at war with them, we just needed to declare war to take this region. But really, we're still friends."
I like the thinking behind this and we could even make a new rule out of this.
Basically, I think it is time for a rule that says "if you do things in-game, mean them the way you do them.". Which means if you duel then it's a duel and not a training match. If you challenge someone for a death duel, you really want one party to die. If you create a religion, it must be a religion, and if you declare war you really want to bash in some heads.
I think the "do what you mean" rule would be easier to understand than a "don't do things purely for game-mechanics" one, while meaning pretty much the same thing.
