I just want to make sure that I have this right: If I create a character that helps out my primary character, and give basically the same ammount of care to their individual developments, then they'll both be considered full-fledged characters, right? I'll get to make a bio for the other one, and send him out on missions and such all by himself? And it doesn't really matter that my account is named Smarts, right?
Typically most people create multiple accounts for different Played Characters (full-fledged characters, as you put it), however you can simply use the same account if you wish.
It's all a matter of what you prefer, really.