I completely agree. I have been thinking about what parts would be worth including but really need to go back to rewatch the earlier episodes (and the film).

I think my ideal scenario would be to have Obi Wan be the central character. Have Dooku as the main villian throughout all three, supported by Grevious, Sidious (who would not obviously be Palpatine), and Tarkin. Keep Yoda completely hidden. And make the love story much better without being too big a part of the story.

That said the only part that springs to mind from the episodes is when Coruscant gets attacked and we see buildings blowing up, I think that would be worth including. It is a shame we aren't likely to get any shots of Vader that would match in style, or that we can't somehow mix this with the newer cinematic videogame trailers (The Old Republic one also has some great shots of Coruscant being attacked).

Would you keep Ahsoka or cut her out altogether?