Hey.
So, I came up with two little ideas that could imo do really good for the game:
1) Auto-closing doors, and here I mean the small doors inside the castle, not the huge main doors. This way you can stop worrying about your teammates leaving the doors wide open: if someone opens it, it closes after one or two seconds.
2) Prevent defenders from opening the main castle doors. If they want to go outside, they can go by another way, and why the hell would they want to go outside anyway?
These two things would prevent defenders team from losing early due to betrayers or idiots. Imo it's just common sense to prevent a lamer to open the doors to the enemy.