I understood the original request to apply most prominently to noble trains. If you send 5 nobles and it's taken in 4, you will not end up attacking yourself. I'm not sure how this would change all the intricacies of gameplay, but think it might be worth a bit more discussion.
With that being said, I think I would still have to disagree. I know I've seen strategies where a defender will lower the loyalty of a village enough that when an enemy nobles, they end up losing troops as part of the defender's strategy. This whole aspect of defense would be removed from the game.
I believe there was a suggestion at one point for an additional feature to the Tactician where your forces will turn around and come home if your first nobles took the village already. Perhaps I'm mistaken in saying so but seem to recall something along those lines. This might be a better route.