On the topic of multiple characters per player:
You generally need to have some sort of structure to the game that facilitates such a thing. Just having multiple characters without such a structure can create issues.
Ars Magica is an example of a game that is set up with multiple characters per player. Each player controls a magus, one or two "companions," and a handful of "grogs." Companions are heroic characters with great skills and abilities. Grogs are servants who are often only minimally talented.
You switch between which group you're playing at any given moment. You might play a magus leading an expedition with a number of companions and grogs one session. Then you switch back to the grogs who were left behind in the base of operations and play a light hearted interlude the next session.
It's actually pretty clever. I could see something like that working for Dresden Files, where the players make up some sort of organization and play various members of it at any given moment. It could make for an interesting game.