I've been thinking about the way I'd do the TV series. Here's a little bit of what I'd want. Ideally it'd be a 2D-animated series with 12-episode seasons.
[spoiler]
Season 1: The first episode would be very similar to The Invasion. In the battle at the end, a Hork-Bajir would scream the name of a fellow warrior as its friend dies, giving a slight implication that the Yeerks could be deeper than Elfangor said. These little things would continue throughout season 1. In the penultimate episode, that would come to a climax with The Departure. Cassie's butterfly-ness is permanent, however. The finale would be AC... without that weird Time Matrix alternate universe and wheel monsters.
Season 2: The last third or so of the season would start with The Decision, but the characters would get into space differently. The characters would stay in space for more than just that episode, though. They'd be stuck out there, and be taken to the Andalite homeworld. Why weren't the Andalites on Earth? Well, it's because their last troops were at the Battle of Leera.
Most of the homeworld is controlled by Yeerks.
The Animorphs and Andalites put up a good fight, but not good enough. The Andalite homeworld is destroyed. Few Andalites survive. The only survivors (save for Ax) are turned into Controllers.
Too different? Maybe so.
Season 3: Episode 1 is a double-length episode. The first half would be similar to 45, minus the contact with the homeworld, of course. The second half is basically 49. We have the final arc, and everything's the same except that the losses for humanity are bigger and we have the V3 VS Ax thing I've mentioned before. Also...
Ax leads a group of humans on an mission to the Andalite homeworld using the ships they stole in the S2 finale. No one returns; the Animorphs investigate. They cross paths with the Blade Ship. It is holding the crew of Ax's ship. They have Ax hostage, still (relatively) free. They tell the Animorphs to retreat - we'll mind our own business, thank you very much. They're outgunned and all that, but the Animorphs stand their ground. The controllers threaten to kill Ax if they don't leave. No one moves. Ax is killed.
See, at this point, the Animorphs can't let the Yeerks skate by. With all that stuff left on the Andalite homeworld, they're free to take anything that works. They could rise to power again.
"Ram the Blade Ship!"
Both parties are killed.
The Yeerks are dead, but so are the Animorphs. Who won?[/spoiler]
Does this suck? Probably. Is it full of plot holes? Probably. Do I think about changes I would make way too often? Yes.
I'd love you to throw your opinions/suggestions/bricks at me!