I want to write a grown up RPG, not an "adult" one as such, there are already plenty of those. Some are good, some are not so good but for the most part they're much the same as your regular RPG except with more tits and swearing. Most RPGs feature a bunch of characters with no real ties to the world and nothing much to fear, sure they're subject to the law in the same way as the rest of the game population but that's about all you can threaten them with. We know now that monsters aren't real, many of us are grown up and have kids or loved ones and aren't afraid of the shadows behind the door or the creak in the dark. We're safe, we know we're safe and we know that at the end of the session we're going to go home to our safe houses in our safe beds, secure in the knowledge that the nephandi or vampires aren't outside our window waiting for us to put out the light. I want real characters with real lives.
I want to write a game that, at the end of the evening, makes you walk a little quicker from the bus stop and check behind the curtains before you go to bed. If I can do that then I'll be a happy man. I want a game about madness, blood, piss, shit, human evil and that dark little monster inside us all.
Of course, right now what I want to do is finish the God-damned rules so I can get to the meat.
That might sum it up.