Culture used to be derived from the mother, which led to future generations of nobles being rather diverse. I enjoyed that and played with it by having my OG male marry a woman of another culture, then continue as their daughter (since women can't be arranged to marry without them leaving so you maximize family members by playing as your daughters/granddaughters/etc.) to have kids of that culture who can maintain loyalty of said culture's cities. Now it's derived from the father, which will change how I play since, as much as I enjoy being a Battanian, I think they have the worst aesthetics in clothes, hairs, etc. and would rather have my kids dress up like Vlandians, Imperials, Aserai, Khuzaits, or literally anything else since you can't just take your kids to a barber when they grow up.
I definitely agree about marriage arrangements; I'd prefer it if clans could be independently allied with one another and for that to carry real gameplay weight. You'd have an actual reason to send out women from your family rather than horde them while hoping for boys who can bring more women in to expand your family. I'm more lukewarm about diplomacy because I'm concerned about it being too easy to exploit and enjoy the chaotic uncertainty. A simple compromise would be Warband's 30 day guaranteed peace for every truce.
As for dealing with big armies, that's best done by beating them. Usually, wars go in waves; the first wave is their best and largest while successive waves get smaller and weaker. After about 3 big battles they should be pretty weak, especially if your faction is strong enough to counter-invade them. It's usually around this time that peace becomes preferable by the A.I.--if I remember right--so it tends to be a repeating loop until you're in charge or the balance of power shifts enough that your side can overrun theirs (or the opposite).
