I really don't think there is one concise answer to walls. You have to design a system that defends groups and single players. That alone is a wide disparity. Toss in organized factions vs. just small groups of friends and it get even wider.
First we need security for every door and chest. We need selective permissions on exactly what you can or can not do. Village mechanics are weak. We need to emphasize structure over massive fortifications. Heavy fortifications need to have an expense that limits their use else everyone will have them. We need society/government beyond village.
If Im a single player, merchant, or warlord in the world I should be able to lock my door and chests. This gives basic security.
When we establish claims, personal or village we should be able to define exactly what people can or can not do with permissions. This does not prevent raiders from doing their normal but it does shore up villages for jerks and griefers who join for chaos. It is a reasonable request as a group should be able to assign duties or access. Its a game so we cant always have guards posted as we would in real society. Villages alone need great expansion, rights, and specialized structures or items.
Structures need focus over walls. If Im a farmer who can bar my door and cellar, hide secret rooms, or even have fortified windows to shoot from then even the lowly cabin can be a source of defence. Timber houses become stronger and mansions are nicely fortified buildings. Upgradeable doors from simple to heavy to fortified, and maybe even metal prevent a harder and harder barrier to prevent forceful entry.
If we add new structures like towers, forts, castles, and outposts you create a siege mechanic vs. buildings and not walls. I see no reason why we cant ram fortified structures directly to gain entry. Make it so those breeches can be repaired as well.
With structure you must add new construction materials and grant them each benefits and penalties. Make each good vs certain weapons or siege styles so they all have value.
Make heavily fortified walls, as they are now, the rare defence rather than the common one. The number of bricks for a such wall needs increased, same with metal amounts. And no they don't need more difficulty to breech. The cost needs to represent the benefit. Maybe even only grant them to be constructed by village or even a new level of city. If we look at who actually used to build them it was usually very large groups not a common farmer.
Finally we need society/ governments above village. If you start thinking beyond village you begin to band together society by mutual benefit and need. Why raid the peaceful farmer when you can protect and foster them as part of your faction, coalition, kingdom... You create expanded resource capability by doing this and the ability to upgrade those who defend your realm.
Even new players can grow from this. If they spawn near an existing kingdom it promotes a reason to teach them becasue even a new player can gather resources to help. We create groups without forcing a city lifestyle upon those who do not want it. The rural players contribute to the kingdom with materials or labor, maybe even fighting if they enjoy that. They can scout far faster than a small group as they are in their local areas all the time. They are the backbone of expansion.
If you change the game mechanics to allow society to form rather than hinder it at the village level then much of this random griefing and raiding disappears. It becomes kingdom vs. kingdom. It balances its self because the kingdom head who does not protect and foster those in his or her realm will quickly see resources dry up , allegiances switch, and outright revolts that tie up your warriors. Unified kingdoms become stronger.
We then change raiding to focus on towers, guard posts, forts, castles, and fortified cities. Risking war with a kingdom to raid one farm now becomes deterred for fear of retaliation on a grander scale.
Along with these steps you begin to truly allow trade to flourish much like the Hanseatic league. Trade towns or cities can form. Those same military buildings can serve as trade houses.
The discussion is about walls, I know, but their change and removal affects a whole change of things that have long been unaddressed. I knwo this has become a book of text and I say this alot but Variety!!!!!
