The issue with native secondary castles is not as straightforward as it seems. Let's imagine one player has two different castles, while another has two identical ones. The first player builds an army everywhere and plays with both castles, while the second frantically worries. This is also unfair. There are two options: either completely prohibit developing secondary castles for troops (which would undoubtedly impoverish the game), or when a native secondary castle is found, the opponent must notify the other player, and a mutual ban on building an army is imposed. At the same time, any other castles can be taken.
To be honest, I didn't even think about that. Regarding notifying each other, it would be too complicated, and then it would be difficult to prove anything, that you notified him. We need to come up with something else, either for the one with the native secondary castle to look for another non-native one :D or take one from the opponent.
But now this will affect a much smaller number of games and players.
Well, the ideal option is, of course, to come up with something optimal.
Charity suffereth long, and is kind; charity envieth not; charity vaunteth not itself, is not puffed up,
Doth not behave itself unseemly, seeketh not her own, is not easily provoked, thinketh no evil;
Rejoiceth not in iniquity, but rejoiceth in the truth;
Beareth all things, believeth all things, hopeth all things, endureth all things. Charity never faileth...