Wow, you guys are ripping on Yorick pretty hard. What's wrong with discussing the impossibility of an Ani-TV series/movie? It's nice to dream, isn't it?
Anyhow, Yorick, I have issue with a couple of things. The two biggest being: Tobias regaining his human form and the new ending.
I agree with wotw. This is a show that COULD be directed at an older audience easily. If it was sold right. You would have to make the characters a bit older (16-17), and obviously you would sacrifice some of the original story. However, it could be done, I suppose.
I do think that at all costs you need to maintain the original structure of the story. This means all major plotlines are included: Invasion, Tobias' nothlitism, Marco's mom, Ax's obligation for revenge, the Chee, David, the entirety of the final arc: including the ending. In a darker series you do not have a fluffy ending. It doesn't fly with the rest of the book. Other aspects that I personally think are important to include:
Elfangor's backstory
The Yeerks getting the morphing cube
Tobias being tortured by Taylor
The fact that not all Andalites are good (a la several books)
The rivalry between V3 and V1
By changing the ending you're changing Applegates message. Which I personally believe is something you should NEVER do when adapting a book or book series.