I've been doing a lot of thinking about the Animorphs ending, how much I hated it, how much I hated that push for Remnants at the end, and all that jazz.
What if The One were like a reset button?
I thought #41 was dumb and pointless the first time I read it, but I realized how much I liked it the last few times I've re-read it. You don't figure this out until the end, but it's a test for Jake to decide whether or not he would save Cassie or save the world. He ends up choosing to save Cassie, which makes this unknown being even more interested in Jake.
Let's take a look at the last book now. Rachel is dead, Tobias is depressed, Jake is tramautized, Marco lives a shallow life, and Cassie is like "whatever, I have a new boyfriend".
Then Tobias, Marco, and Jake go into space to save Ax.
Assuming they die, doesn't their sacrifice mirror Jake's sacrifice for Cassie? Jake knew he was going to die in #41, but saving Cassie was what was important. J/T/M's mission was basically a suicide mission, especially when they took along students that didn't have family.
If the being at the end of #41 is The One, it certainly has the power to revive all of the Animorphs. I'm also going to assume that The One is the being that expelled Crayak, as referenced in the Ellimist Chronicles. If you're powerful enough to get rid of Crayak, you can certainly bring a bunch of teenagers back to life.
I was thinking about this because at first it seemed like a really dumb way to end a series. Introducing a brand new character in the last pages of the book is normally really stupid, especially when it doesn't bring resolution. However, #41 was also totally unexplained. It's usually written off as a filler book, but I don't think it's like the Nartecs or Australia - which both have significance, but whatever.
What if this were a way to tie #41 into the series continuity and just wasn't done as well as it could've been?
I'm not going to want to read a wonderful story if it ends on such a sour note. But what if this were a way for Animorphs to have an unhappy ending and a happy ending at the same time? Like they have all of that suffering but it still works out in the end because they come out of The One with their memories buffered (minus Rachel) and resume their lives right after the Pool Ship? Or they've been taken to the Pool Ship with the knowledge they need to win?
Why else would she have ended it this way?