But if every character gets the dreams, that would make some storytelling content static.
That depends on how it's done. Every character gets dreams in the first two installments of this series, but different things happen in them - and as a result of them - based on decisions made as that character.
That was my initial point about it as well. Every character gets dreams to creep the players out and to press home to players that they still have a tadpole messing with them. However, if you don't use tadpole powers, these dreams are less frequent than if you use tadpole powers. Maybe offer different dialogue options during the dream sequences too. If you don't use tadpole powers, you resist the dream person more in the cutscenes. If you use tadpole powers, your dialogue options are more geared towards succumbing to the dream person's advances. That sort of thing.
