As for the precognition: If Celestia could see the future, the fic would turn out extremely differently.

She could have a variant of the Pinkie sense - uncontrolled limited precognition. Or it could be that there are feedbacks such that in order for it to work she needs to avoid all involvement in the proceedings (which is why she works through agents so much) - and introducing an endemic threat would require her to basically recuse herself from her own civilization, which seems a bit much.