Make Palpatine an ancient sith. Deepfake his face. Redub his lines and add new lines.
This new character is an ancient sith who was snokes master.
New lines of dialogue should be added along the lines of:
"Long have I waited in the shadow. I have watched the jedi rise and fall for over a millennia. I have seen hope grow and decay, all in the same breath. But through it all, there has been a constant, that constant is the dark. "
Yadda yadda etc etc…