It doesn't feel like errand running if you can do whatever you want. Besides you can go explore or do something interesting yourself. In fact I'm trying to make this less railroady. If you look at it that way, everything with a goal is an errand. Besides helping factions isn't 100% necessary. You can learn spells from artifacts or by stealing or otherwise obtaining magical scrolls. In fact the mechanics would be made to encourage gaining various powers rather than sticking to one faction and gaining all of their powers. Getting the strongest spells should not take much time or effort - it's more about variety.
I guess what I mean is that it sounds like the world will be somewhat crowded, so there's not necessarily a lot to do with your power/money/influence once you get it, other than maybe pushing other people out of your way to more or less do the same things they were.
Not necessarily "shorthand". Since everything requires rolls in RTDs it's just a different way to solve problems. It's not 100% effective and it's not 100% necessary/superior. Besides, sounds more interesting that just having a set of damaging spells, buffs and summons. Though you can have those too. If you want to, you can just go 100% combat and cause random mayhem.
Well, that sounds neat then.
I don't know a lot about World of Darkness. In my mind it's more like E.Y.E./Deus Ex with less cyborgs and more magic.
I don't know anything about E.Y.E. or Deus Ex, other than that I really, really need to go play the latter.
As for suggestions, you need to make sure YOU like the game as much as your players, or else you'll lose interest and it'll die.
That said, I've been thinking about mentioning this for a while, so I might as well rattle off all the things I was thinking about running. Maybe you can get some inspiration/insight from that, maybe not.
Setting is more or less DF with all manner of bizarre things thrown in. Players can be any race they want and still probably be normal enough for it not to seem strange that they/their ancestors were absorbed by the dwarven empire they're now a part of. They're then sent off to die found a new fortress.
Game is split into two parts, usually running simultaneously: Fortress Mode, and Adventure Mode.
Fortress Mode is a weekly schedule, with one turn being one week. Each turn thus has seven actions, and you need to eat/drink seven units per turn. All crafting actions for the week use the same roll per person.
Adventure Mode is basically an RTD with a different combat system. Players go explore caves, fight ogres, and generally just adventure around the miserable hellhole they've chosen to colonize.
Players gain experience in skills using a very simple system. Starting profession also gives a starting boost to some skills and a penalty to others. Skills are mostly identical to DF ones.
Players play as young "themed" adventurers. Foresty, dark, fiery, whatever. "I come from the X Village" should mostly sum it up.
The world has that sort of simplistic smallness that doesn't make a lot of sense if you think about it too hard. Maybe there's a grand total of two settlements you're aware of in the whole world, and only one is large enough to have a blacksmith. Yet there's mindless skeletons sprouting like weeds outside when it's dark, which probably isn't explained very well either. It probably goes without saying that there's massive, sprawling stone temples everywhere when the best builders you know of can't manage much more than a wooden shack.
Items follow a similar style, in that they're reasonably rare/difficult to get, but usually fairly permanent and useful once you get them.
Plot is probably pretty much collect all X shinies to prevent/bring about/flavor the apocalypse/nice sword/changing of seasons, with the players being presumed to be rivals/not working together, but not really being prevented from such except by conflicting goals and maybe politics. Players could also have other goals, like gaining a shiny new mount or starting up a new settlement or something.
Mechanics are mostly standard RTD, with items letting you do something at all or giving a small bonus to the roll. Skills probably wouldn't exist too much, but you might get some sort of skill/trait/thing for being especially good at something.
Players play as demons or similar creatures, formerly in the employ of some demonic overlord, that have been somehow shunted to a somewhat Minecraft-esque world, in that they're in the middle of an open field and there's absolutely nothing here except a lot of trees and certain death come nightfall. Plus maybe a handful of minor villages, which are little more than a gathering of hovels and who aren't even savvy enough to know there's something wrong with you. Players then proceed to build themselves up so as to not die, then start working on whatever other goal they choose to have, be that getting back home, claiming the land as their own, corrupting the locals, fashioning themselves a sweet sword prior to doing one of those other goals, etc.
Mechanically, mostly basic RTD stuff. There's probably some stuff I'd have to consider more carefully, but the idea is to keep it simple and in largely handwaving RTD fashion.
Players play as the leader of their own faction of elves, knights, demons, undead, etc., and proceed to battle neutral creatures, hostile NPCs, and each other in their pursuit of power. Heroes and the players themselves gain experience and level up. Minions probably do the same, but that might depend on whether your soldiers are single, identifiable units ("Bob the Infantry, go block that troll") or larger stacks ("Pikemen x50, go block that Troll x4").
Otherwise, no idea.