Ever. I mean...okay, you don't want to kill Alloran while he's slowly dying from poison. I get that.
So acquire Alloran and have a morph you can use to really screw with the Yeerks.
That's not the only instance either. We learn in book 8 that Ax can acquire animals with his tail. He tail fights with Visser Three a couple of times following book 8. We know that animals don't always pass out when they acquire someone, so I wonder how many opportunities did Ax have to acquire Alloran.
And before you remind me about the "no sentients" rule, remember that was only the Animorphs qualm. A qualm they forgot a number of times through out the series when the situation was desperate.
And if not Ax, why couldn't Tobias find an opportunity to land on Visser Three's backside, the one are where he would be ostensibly unprotected as he duked it out with Ax. And no Yeerk would be desperate enough to kill an Andalite that they'd fire on Visser Three. (Unless it was an assasination attempt by another Yeerk, but lets assume for the moment that V3 is accompanied by trustworthy elite controllers) Tobias, post book 13, acquires Alloran, Visser Three may or may not trans out, thus giving the Animorphs ample opportunity to kill him.
Even if he doesn't trans out, now Visser Three has to live with the fear that somewhere on Earth is an Andalite with the morph of his host body, who can subvert commands and cause chaos among the Yeerks. Even controllers he maintains regular contact with can't inform every single Yeerk on the planet that an imposter may be on the loose, so that causes a bit of stirring.
Thoughts?