The only way I can think of deflecting attention away from Anakin as Vader is to merge Grievous and Maul together and redub them so he becomes an ongoing nemesis for Obi-Wan in the same way that Vader is for Luke in the OT.
Maul is a man of very little words in the official versions and Grievous is a man of many words which sound rather silly.
If new dialogue was written which made one character out of both and made him obsessed with Obi-Wan (the only knight to best him) you could paint a picture of a defacto pupil (someone who studies him from a distance) but even that doesn't get over the "BEFORE he turned to evil" part of the equation.
It would be fun to replace Fett on Geonosis with Maul Grievous, it would make more sense in terms of story but it's hard to believe he wouldn't leap in and fight Obi-Wan again (it would be too much work to get Maul/Grievous to take over the saber fighting from Dooku).
It did seem strange that Maul dispatched a Jedi Master with some ease but came a croper to a Padawan.
If he survived that could turn into an obsessional study of the techniques of the one who beat him.
