[@MatthiasAngel]

Here's an idea:

The characters we play as are actually the in-game avatars of the players actually playing the game, or something along those lines. The game is in open beta, so a bunch of players sign up, create characters, and jump in.

As for the end goal, how about something along the lines of the game itself being revealed as malware created by the game's developer, and the players' goal is to find the main core of the program through some sort of debugging or something similar, like a glitch, and destroy it? It's a bit more complex so it might not be what you're looking for, but I'd at least give it some consideration.