[iago]

I'd suggest that taking a close look at stunts may fix some of the "differentiated threats" issue. Stunts are, intentionally, where a lot of the *mechanical* differences between characters can express themselves -- the rest of the system uses a fairly small number of common "interfaces" for enacting effects on the story. So if you're a sim-head (and there ain't nothin' wrong with that), you gotta get friendly with the stunts.

For what it's worth, the Dresden Files RPG may offer a fair bit more in this regard.