I'll tell you what we'd get...NEOMORPHS!
Alright, then... What if the Finale Arc had started with #55, which would have been narrated by Tobias?
Would any of the plots from #45 - #54 have happened? What effect would the narration change have on the series from #45 - #64?
How would Loren play into the beginning of the 55-64 finale arc?
(Note: At one point, Applegate had an 80 book contract for Animorphs, which was shortened to 72, then to 64. However, she also had three missing books in the contract: Megamorphs #5, a fifth Chronicles and the Series Bible.)
Edit: If my theory is right and the person who was supposed to narrate the final book dies not matter what number the book had, than it would be AX dying in #64.