Yes, I meant that if a companion slurps the tadpoles, they just should get changed by Orpheus or Empi.
In my case: if Minthara is my slurper and I have her with me while freeing Orpheus, he should not even ask, just change her, because she is already mostly Illithid.
Wouldn't it be very unhelpful though?
In case of the domination ending (I'll just leave the spoiler tags out of it, I assume everyone reading this is well spoiled by now) it would make sense to me if both the player and their partner (maybe also the other companions, if they are part of the scene) had to resist the Netherbrain. The brain wants to regain control and if it fails to subjugate your character but manages to take control over your character's partner, it can then use them to fight you to either lower your defences or kill you.
Empi has already shown that he has no qualms to help you reach your potential against your will at the start of Act 3, but he seems to prefer taking Orpheus' power for himself. So why should he force anyone to transform at the last moment? To have stronger allies? It doesn't sound such a great idea to destroy your allies' main motivation for survival right before the final battle. Yes, there might be players who want to save the realm before all, but I feel most take the neutral stance of wanting a good ending for themselves and their pixel friends.
And Orpheus seems to only accept your proposal if it is a no-way-back commitment situation. It's why he refuses the Orb unless you assure him of a back-up solution, Gale might decide he wants to live after all, but if you have turned into a mind flayer, your fate is sealed. He does not seem to take back-stabbing into account though, which is odd given his distrust and initial hostility towards the player.
Stakes and consequences are all good and well, but I generally prefer a longer build up for choices so you can brood over the decision, instead of these last minute astral jump scares. For example, I love how in Gale's Origin, Mystra reveals that only the orb can truly destroy the Crown. Detonating it would be that ultimate sacrifice for the Weave, while delivering the Crown to her is only a compromise. Right after being given a way out, this heavy burden is placed on your shoulders and it follows you all through Act 3 - and I loved that.