So we don't know much about the game as of the time of this post, but we can safely assume that (a) we will be creating a singular character as a PC and (b) we will be a "Watcher" of some sort.
We don't know how the game will start, obviously. It could go one of two ways. One, you have a lot of control over character creation but your past as a character is either fixed and part of the story (BG games) or not even really bothered with at all (Elder Scrolls games, IWD). Two, you show up in media res, a grown-ass man / woman / myconid, and you have some control not just over the appearance and skills of your myconid, but your myconid's background. Usually it's something like NWN2, which were sort of akin to minor Fallout traits, giving negligible bonuses and penalties to stats, and maybe eliciting a comment from someone once or twice. But there are exceptions: The content for each Origin in Dragon Age was pretty substantial, though it has less bearing the more you go on in the game.
My personal favorite, though, was Arcanum's system. You went beyond mere socioeconomic and personality-based backgrounds toward the weird and fantastical. You could be a Frankenstein's monster, a magician's assistant, an idiot savant. No original game content was made for any of them (though that could change in a revisitation), but they were outlandish and what's more, they generally affected your stats in dramatic and often unchangeable ways, as well as put you in weird situations no one else would be in (freaking out in the sewers as a hydrophobe, for example). As such, they could substantially change the game.
Does the hivemind agree that character backstories are cool things to pick and choose for a character, provided he/she/zhe is not set in stone from the outset? Perhaps you can choose what it is you were doing when you were conscripted into the Watcher role, as it sounds like you were.