Konkistador could make a retal only go thru if the previous attack is made by the same province otherwise the protection will still be valid and therefore the retal rights cannot be used until the Kingdom is oop
This would encourage castle passing = attacker takes a castle from you, then has their buddy in a different province attack them, now your retal is void and the attacker is safe from all.
I guess castle passing is a response to pre-re. To prevent pre-re, you castle pass so you'll only face a retal. If you don't castle pass, then you face the possible pre-re. If we add functions to discourage just one, then the other will flourish to either benefit the attack or defender.
If we got rid of retals, then castle passing is buffed, because an attacker can suicide attack, then pass the castle to a friend for free to gain protection.
It's complicated, and so far I haven't seen anything remotely close to solving the problem.