The emphasis on Anakin is the single biggest mistake in crafting the prequels IMO. Anakin needs to be a smaller part of a larger story so that Darth Vader's "destiny" is no longer so over emphasised.

That's why giving other characters more important stuff to do is needed in my opinion. Obi Wan having a nemesis would make his story that little bit more interesting rather than the role he has now (bad detective filler)

...but that's just my opinion. Most of the ideas for blending Grievous and Maul are probably too ambitious anyway :)