Being whoever you want and having complete freedom in regards to character isn't a major selling point in Bioware games though; well not ME anyway, and maybe wouldn't work so well even if they wanted it to be, unless they make changes to the type of game ME is, and its style. You have to work with what's already established about the character and go from there.
Agreed. And to be honest there's no game out there that has the "be whoever you wanna be" thing on it, simply because the devs have to build a storyline around it and there's so much "freedom" you can get.
Not even Bethesda games (by a long shot).
Fallout 3 for instance: you lived on a vault and left to chase your father, stuff happen in the middle. Same thing for the next playthrough and the next, and the next. Although it was cool that you could choose to be a evil(ish) character.
FO4: even worse. Vault dweler chasing his son. Plot twist and boom, the guy who chooses the fate of the commonwealth. Who would have thought.
TESV: you do not known a thing about you past as a character (bonus point here), but it just so happens you're the mother effing dragonborn and have to save the world, you're a hero whether you like it or not. Same thing for all playthroughs.
The best possible scenario is a good story with some interesting variations for different playstyles.