A couple of suggestions I have about adventure mode, I assume other people have made suggestions like this as well (and I imagine some of these are already planned):
1. Slaughtering entire towns shouldn't be unnoticed and unpunished: players should be able to become enemies of entities by commiting crimes against them, gaining notoriety similar to megabeasts and bandits - people might hunt you down for killing their relatives, even if they're civillians and not soldiers, and other adventurers you play as might gain quests to kill other adventurers who've gone rogue. Consequently, enemies of the civilizations you've angered will treat you as an ally.
2. Being able to hire mounts like horses or any other mount used by a civ to travel faster, maybe adding more possible attacks while mounted.
3. This is less a adventure mode specific suggestion and more of a general one, but adding more possible attacks to wrestling that you can learn when achieving higher skill levels, like driving your opponents head into the ground, snapping necks, piledrivers, or tearing off limbs (and perhaps organs) if you're strong enough. Perhaps similar could be done for other weapon skills, adding new ones besides, for instance, regular slashing and stabbing.
4. Aiming throws and ranged attacks at specific body parts, also aimed wrestling throws.
5. Being able to craft items, weapons, decorating items with bones and other parts. Also adding objects that add more attacks to weapons, like spikes to shields that allow jabbing. This should also be added to modding so that things like shields can have more attacks by default other than striking, and items that are equipped and not held in the hands could also give additional attacks, i.e spiked gauntlets that can cause puncturing damage or horned helmets that allow goring.
6. NPCs eating and drinking - so you can, for instance, you could join people in taverns and get royally plastered to celebrate killing a megabeast. Also, to add to this, you could poison someones food with snake venom or forgotten beast extract in order to kill them more discreetlly. Extracting poisons would be a skill adventurers could start with or learn.
7. You should be able to get positive notoriety easier, especially for killing megabeasts. Also lords and other officials should be able to join the player if the issue of the matter concerns them personally - it's somewhat jarring to learn from a lord that their son or nephew has been kidnapped, yet when you ask them to join you in order to save them they say they have no interest in your objectives.
8. Zombies raised by friendly necromancers should also be friendly to the necromancers allies instead of trying to kill everyone. Also, zombies should be able to take orders and equip items. Perhaps add a tag that lets creatures understand orders even if they can't speak? That would also help make way for taming animals. Also necromancers should have an interaction that lets them instantly deactivate their zombies - basically it kills them without damaging the body.
Right now that's all suggestions I have, I'll add more when I think of them. Feel free to express your opinions or add ones yourself - I'll attach them to the OP.