a completely freeform faction camp system, with the ability to go "i want a building here, of this size and shape, made out of these materials" paired with the ability to declare "this building needs to be a housing/workshop/storage area, fit for these purposes", ultimately resulting in "my faction camp 'missions' are completely derived from the actual constructed amenities currently in service, rather than pure abstractions that have buildings as a side effect"
That's really tough, there are a bunch of huge features that might not happen outside of magical intervention.
Probably the hordes system and associated subsystems like fire spread and NPCs roaming around scavenging things.
The thing about a proper hordes system is it essentially makes the active area of the game bigger, so now you have to worry about things in earshot and things that you previously interacted with instead of just things you're looking at in the moment.
while i definitely want hordes most of the things you'll hypothetically get to someday, i was really excited for a little while at the idea of the sun tracking that almost happened. that sounded so cool (and with our increasingly viable 3d fov stuff, could LOOK cool in our modern rendering)
An abstracted patrol system that creates a sense of dynamism outside the reality bubble. For example when a migo scout tower is spawned a path several map tiles away around the tower would be generated (not visible necessarily to the player). A group of migos would patrol this path, importantly they wouldn't just be a random spawn, the game would keep track of a value for where the migos are on the patrol route (in an EXTREMELY abstracted sense of a single value for how far along the path the patrol is in terms of time, not actually somehow pathing each migo outside of the reality bubble) and if the player happens to cross the patrol path when the migo patrol is calculated to be at that point of their route then the game would spawn in a migo patrol. The migo patrol would spawn headed towards a series of waypoints that lead out of the reality bubble in the direction of the patrol route.
If the migos spot the player or another creature while in the reality bubble, they would break off patrol and attack. One of the monsters would be designated the "captain" of the patrol and once the captain drops out of the reality bubble from the player running away a timer counts down (say an 15 minutes) at which point the patrol despawns and the patrol route progress parameter resumes counting. The patrol routes wouldn't have to be actually feasibly traversable, who cares if the patrol spawned in and got blocked by an obstacle from proceeding, the patrol would just despawn 15 mins later and continue abstractly along the patrol route.
To keep calculation simple, disturbances to the schedule of the patrol routes wouldn't even have to be tracked, they could just be reset after the "disturbed" patrol despawns. Patrol routes progress also wouldn't have to be stored and tracked permanently for every instance of a migo scout tower (or other monster patrols), they could just be forgotten once the player is a certain distance away on the overmap and began again once the player enters the region again. Destroying some piece of equipment in the migo scout tower or killing a "commander" migo in the scout tower could delete the patrol route from the game files.
The reason I want this is because I love the idea of creeping up to the edge of a field and seeing it is clear at the moment, but knowing that I have seen migo patrols go by in the past. I could then lie and wait until I saw migos pass by and then continue after they passed knowing I was safe to cross or chance it and cross sooner if time was of the essence. I want open spaces to feel vulnerable to enemies stumbling upon me by accident (in a way I can't easily outrun) just because they were passing by but I don't want it to feel unpredictably random. I love the idea of having to sneak across a busy, dangerous patrol route.
Further down the line a skill of tracking could be added where the player can perceive the well trodden path of a patrol route and perhaps how long ago creatures passed by on that route.
When I have suggested this before people always freak out about how silly it is to try to extend the distance of the reality bubble (exponentially increasing calculations and all), but this isn't really doing that, it is more like just keeping track of a single "patrol route progress" variable for each path, and only paths in the same general region on the overmap. No other information would have to be calculated outside the reality bubble.
What you're describing would probably be a subset behaviour of a proper horde mechanic. Proper wandering hordes would allow us to have mobs move around the map without being loaded into the reality bubble, using a much simpler rendition of walkable paths. We need it for a lot of things but it is one of those "very tough to implement" things that needs a really knowledgeable coder with a lot of time.
Proper caching of the contents' volume and weight in the pocket. Many of our systems are not designed to process items in quantity, which means when there are a lot of items ( lets say 4000 or so ) in a pocket, the game can be stuttering when doing certain activities ( opening insert menu, wielding item, etc ). However pockets are often interacted with from high above the call stack thanks to item_location :P. So tracking the contents change is very hard.
Procedural New England mapgen where all the geographical features are in the right places and cities the right sizes, but the details differ every time to keep things interesting. If you're familiar with how UnReal World does it, essentially the same idea.
This would be awesome. Personally I'd still prefer a fully procedural mapgen that mimicked the look of a new england area state, but it's looking like new Massachusetts is more feasible