noname_marco
Just let your MC become neutral to Nie lie because having Nie lie alive is a great help when dealing with sage emperor. And as you said he is an original personal person of his own not a copy of Nie lie with his knowledge. And instead of acquiring or stealing temporal spirit book why not just give your MC an equal or more powerful cheat on his own a cheat that relates to his uniqueness aka (Buddha) you're the mighty author after all. Well this is just my own opinion.