It sounds like fun, and normally I'd volunteer to edit down the books since it's the kind of thing I love to do, but I really don't have any time to do them all. Why not have a group of editors work on individual books? If ten people worked on the series at once and compared notes, it would be much faster than having just one editor.
Also, I would recommend skipping the "filler" stories whenever possible if you want to actually finish the project. This series is huge. It might even be a good idea to take some liberties, too. For example, instead of introducing Drode in "The Exposed," it might be better to skip that book (which would also allow skipping "The Mutation") and have Drode pop up in the next book where he's relevant.
Before beginning, it would be a good idea to take note of when morphs are acquired and used throughout the series, especially if books are skipped. Let's say (and this would never happen) you choose to skip Book 3. Well, the Animorphs need to acquire wolves at some point anyway, so that scene would have to be worked in. Too many "Oh I acquired this off screen" moments would hurt the comics.
Re: a few of the comments about art style
I would have to recommend an American art style for this. I have nothing against manga at all, but I just can't see a Japanese style working for this series. When I think of Animorphs as a comic, I think of a style similar to western superhero comics, more realistic than cartoony. In any case, making it read right-to-left would be silly, as English is meant to be read left-to-right.
