Well, it circles down to Anakin being "a good man and a friend" - we need that in at least one whole movie, it is rather frustrating only to see Ani to be a warped picture of Luke ...

@shanep

one way is to bring the "Vader" into play, and create a disruption within the Jedi order - the "lost 20" story is a nice vehicle to get this through ;-)

the combination of Qui-Gon & Dooku might also work, if we have him be a mentor friend of Obi-Wan and a forshadowing of what could happend to his own pupil ...

can't remember if it was proposed here, but I think if we keep Anakin/Vader as just one person, a intersting possibilty could be that through the horrors of war, he spilt personality, and now the dark shadow is hunting and trying to kill all that is dear to Anakin (read this like a Jekyll/Hyde plot)

another point is how the "dark side" corrupts a Jedi, the "saving loved ones" isn't working for "Sith" - it should be more about personal power!