ProfessorCirno,
A question, what if they don't take any of the "jobs?" What if they just run around picking fights with random monster for a few levels?
I'm sure you've already covered that kind of player choice, having their choices impact events they encounter at heroic and epic is a perfect method for managing a "living world." It sounds like you've put together a well laid out system to keep you head of player choices in world logical fashion. My questions are really more illustration of the difficulties in creating a responsive sandbox. It's actually far easier to make a reactive sandbox in a Pen and Paper then in a computer, primarily because you have an intelligent processing unit that can adapt and calculate wider world effects of player actions (all us under appreciated, yes?).
They can't, really. Not because I just loom and go "You can't do it!" but because they literally in game cannot - It wouldn't make sense in the setting. There are no random monsters roaming the countryside for no given reason. At best I'd sigh, roll a bit, say "Ok, you get lost in the woods. Roll survival. Ok, you're back in civilization. Really, what are you expecting? It's not like there's mystic ruins to trip over every five feet!"
The only video game I've ever really seen that allowed a player to truly have an impact on the world and setting (plot) has been the Mass Effect line. Although we'll see how all those tangled webs of choices will manifest in Mass Effect 3. Although I wouldn't count Mass Effect a sandbox. Megaman Matrix more like, but done surprisingly well. Now there are some video games to crib some GMing tips from.
FALLOUT.
Oblivion is both a terrible game and a terrible example of a sandbox.
Nothing you do effects the game or the setting. Nothing. Your character might as well not even exist. Even the main question is you walking around and listening to DMNPCs talk to each other. The ending involves you watching someone else fight the last boss.
In an actual sandbox game, your actions should shape the setting itself. In Oblivion, that doesn't happen.
Oblivion had it's share of faults, but I still love the game. I've got at least 5 characters with levels in the high 40's.
In that game, you really have to make your own fun. The ending of the main storyline is a drag, which is why I've only done that part once. When I make a new character for Oblivion, I think about what paths I want to take, what gear, and just go for it. My first character did EVERYTHING, so now I just play until that particular character can do what I wanted it to. Now I pretty much just dungeon-crawl when I get bored.
So yeah, I can't emphasize enough that for that game(even Fallout 3 to a lesser extent) you really have to make your fun. In that respect, I feel like it's a pretty good sandbox, since you can run around the game and explore, gain levels and power, and ignore all of the main storyline. For me, it's also about customizing spells and gear enchantments, and finding all the unique gear. Coming up with new crazy combos of stuff just for fun.
It's not a sandbox because there's no sand. You can't build a sandcastle and admire it and then do other stuff with the sand and make a big sand city because the game doesn't recognize anything you do. No matter how you play the game, every time you play, it's the exact same, because there are no choices to make.
It's an empty field, and you're sitting in it and pretending to play with sand.
Now it seems like game designers are trying to incorporate this concept into P&P.Sandbox was always there. The novelty* is that people now try to incorporate this into modules.
*My knowledge about older modules is not very extensive, it might well be that this has been tried before, but I'm only now really seeing it in smaller scale in modules like Seven Days to the Grave and in grander scale in Kingmaker.
Kingmaker is, in essence, a much expanded and modernized version of the module CM1: Test of the Warlords. That module is from 1984 so we have been down this path before.
Really the parallels are striking. In that module you have been sponsored to go forth and explore a new land and found a dominion there. The DM has a map of the new land called Norworld (a northern largely unexplored island continent) but the players just get a outline hex map and must explore the hexs adding in the terrain features that they go. Some of the hexes have triggered encounters with monsters or other inhabitants of this land.
Soon the players will pick their starting city and begin to expand their domain. They will then start to interact with a wide veriaty of NPCs some of whom have charters of their own to start domains in this untamed land. Some events will come to pass like a invasion by giants and such that will require the players to defend their fledgling but growing domains.
It all eventually comes to a head because the PCs original sponsers, The United States of America...err I mean Alphatia, are in a kind of cold war with The Evil Soviet Union...err I mean Thaytis** and both powers have sponsored colonies on Norworld. Eventually all out war breaks out and armies clash in a epic martial contest to decide the fate of Norworld.
**Later Thaytis gets expanded upon in supplements and has all sorts of interesting elements added to it making it a much deeper nation. I actually read those supplements before reading CM1: Test of the Warlords and was rather shocked by how the module portrayed a nation I felt was really rather deep and interesting as kind of cardboard villains.
Oddly enough Alphatia gets a lot of material added to it as well and it goes from being the good guys to a much more nounced nation state that is a good deal less sympathetic. I was surprised when I read the module because I viewed Alphatia as something of a power hungry imperialist nation with a penchant for delving into magic often best left undisturbed in order to harness said magic to crush any who would stand in their way. Alphatia has won many wars mainly on the back of raw magical firepower while their enemies usually find their armies of men with swords are just blown away by a handful of high level mages calling down mass magical destruction.