I see it the other way around. It is using tadpoles that need to have more consequences. You have the positive ones (powers), but there are barely negative consequences to balance it out. From my perspective, the more you use the powers, the more you should want to use them. So past certain tadpole consumption/power use, it should start by changing some dialogues so you can see regular answers but only the "Authority" answer is available to use unless you pass a wisdom save. As in, maybe you have great persuasion and you could have used that, but instead, your proto-illithid brain resorts to power use because that is what an illithid does. And past another point, normal humanoid feelings should start disappearing. Romance makes no sense for illithids unless is to manipulate as the emperor does. And past a certain point, if you have consumed the astral tadpole and many tadpoles, you should crave more tadpoles, illithid brains, and, well, regular brains. Because you are transforming. This means that by the time the emperor tells you that you should turn into an illithid, your character might actually "want" to transform. And resisting that want should be really difficult or even impossible.
Like any other path, the more you walk through it, the more difficult it is to turn back. We see that with Ketheric Thorm. We see it in other characters. Past a certain point, redemption and change become really difficult. Maybe not impossible, but nearly impossible and with a cost. That may very well be to simply die before you are consumed by the illithid personality. Just like the gith prince. That is what was described in early access and what is the threat the characters start with. It makes no sense that suddenly you can turn part of your brain into an illithid but don't change when doing that.
