AdinTheDark I don't think there's anything about that strategy that needs special consideration. If the attacker got hit by his ally to gain protection - they've basically helped the defender by running the pretal for him.
The attacker is in a horrible position, they lost the troops in the attack which either failed or only gained land (making them now fat), then whatever troops they may have had left in their garrison is wiped out from their ally hitting them - driving their economy further into the hole and devaluing the land even more from the spoils destructions, then for a final nail in the coffin the attacker gets retaled by the original defender, thus crippling the attacker even more...
It's 3 negative actions for the attacker in a short span, their KS/army/buildings should be pretty wrecked. I guess the only thing missing to really drive it home would be to hire Trupheus to blast them with a couple Earthquakes š
As far as passing outside a province goes, I'm not sure it's something we should be concerned about. The pre-re and castle pass aren't technically "against the rules", they're just toxic strategies that we want to discourage. If it becomes a big problem and people want a fix, then we could consider features that would make working outside provinces less desirable - like disable sending aid outside the province or something like that.
