Although this is a completely theoretical thing, I think that there are good ideas in here. In other words, I think as highly of my ideas as any other person thinks of his, so my ideas probably have holes in them that I don't know of. And then there's parts that I can't seem awkward but I'm not sure how to fix. I'm also posting this because summer vacation has given me too much free time.
So, when I was thinking about how to make cities, and a couple other things, I realized that I would need to start here. The npc population of a general area is dependent on factors such as safety, available facilities, and exploitable resources (i.e. rare metal mines, abundant harvests). When the population level is high enough in a region, they will consolidate into a city. Constant violence and instability in turn lowers population.
In addition to supplying things such as manpower and tax money to the owner, a city is also trade hub, and is responsible for the safety of the surrounding area.
Each city has a market at which players and NPCs can buy and sell goods. Unfortunately, markets are bound to the city, so the accessibility of different goods varies with the
Cities are able to control groups of npc guards in a certain area. These guards are able to teleport a certain distance in the case that a crime, such as a player going on a killing spree, although the teleportation has a long cooldown such that it can't be used for retreat. The guards are managed through the barracks similarly to how other NPC soldiers are managed.
Different resources (and different crafting methods) are different.
1. They require different levels of skill to use optimally, and thus lower-level materials can result in stronger equipments than higher-level materials in the hands of an average craftsman.
2. They give different bonuses, thus making them optimal for different playstyles and classes. To give an example, a city surrounded by materials which give bonuses to finesse, which is only usable by fencers, will naturally have a higher fencer population.
Crafting is an open-ended process. There isn't a list to tell the player that distilled Lassleworth applied onto a Rebeen plate encased with Stallium can create a battery that stores magical energy, or that Foxweed enhances the healing capacities of a Ironwood staff. This means that players who experiment may find that differing combinations may produce unexpected results. However, there should be a logic to this. In other words, the code shouldn't say "Item A + Item B = Item C", but rather "Category A + Category B = Type C". Think something like how the elements are in an orderly periodic table but that doesn't make chemistry class any easier. One benefit of this would be that an expert player could use his understanding of the system to know when to replace Metalium with Alium in battery crafting when the typical materials aren't available.
Grinding will not be a feasible method of character progression. The exp required to level up will require extended amounts of gameplay. However, gaining exp will not be limited to killing mobs. Exp can be gained in reasonable amounts by crafting or traveling. The exp gained by any activity will eventually slow, not to the extent that a player if forced to take up other tasks to level, but to the extent that
Stats (and Titles)
Players will gain a mediocre amount of stat points from leveling. However, their stats will also benefit from equipment and titles (and certain other things like potion use). Titles and stats are gained from achievements or special quests or instanced events. However, only a certain amount of titles and stats can be equipped at once, generally dependent on the character's level. This means that a player with a wider variety of adventures will have more titles and thus benefit more from leveling, whereas a higher level player will have more slots for titles and stats and thus will benefit more from good titles.
Players who kill other players (and npcs to a lesser extent) will receive sin. Sin increases the death penalty and reduces the amount of sin players get for killing you. Of course, killing allied players next to a city creates way more sin than fighting in a war. Still, fighting against other players isn't free, so even if you can win a war it may leave you in a weakened state.
Players could hire soldiers at cities (although players need barracks or forts to stash them at to control a considerable amount). While players can respawn, npcs are somewhat expendable. However, even if the population of a city is 20,000, you don't get 20,000 soldiers. For one thing, it costs money to maintain soldiers, thus limiting the military force players can draw at any time. In addition, hiring soldiers and losing soldiers can reduce the morale of the npcs, which may make it difficult to hire npcs. Drafting may temporarily override this limit but will lower morale even further, which will have negative effects in the long run.
The game would provide means to command npcs from garrisons and cities by moving pieces on a map.
Events and stuff
While some events may be caused by npcs, players can fill in any role. In other words, a player might get a challenging quest to open a portal to the dark realm, and upon succeeding, may be given control of an army of demons which must be sustained by actions which make life harder for everyone else. Or he may become the chosen hero of the light and be responsible for spearheading an invasion into a new realm.