In The Andalite Chronicles, it is implied (either by Elfangor or the Ellimist, I don't remember) that having these six time lines converge with one another was absolutely essential for the war to be won, which implied to me that the absence of any one of them would have been enough to fail. That's why it was so essential that Elfangor needed to go back to his original time line - that was the only way that the integral six Animorphs would eventually meet.
So, no, I don't think that the war would have been winnable without Ax, for this and probably many other reasons.
I took the above from a thread about wether the Animorphs would have done as well if Ax had never arrived on Earth. This was the last thing posted, and it got me thinking--but not for the first time.
If these six lines were ESSENTIAL to winning the war--and we're told that these "lines" are Jake, Rachel, Tobias, Cassie, Marco and Ax-- then WHY on Earth are we told that Jake and Rachel were "accidents" and not meant to have been in the war? What the hell is that about?
I get the whole "Ellimist chose Marco, Cassie, Tobias, and Ax" thing, because of their involvement in the war, but leaving out Rachel and Jake--claiming that they could have been replaced by any other kids-- just pretty much contradicts the whole theory. What...the Ellimist ran out of options for his game pieces and said, "What the hey?" Rachel and Jake were just "at the right place, at the right time?"