Sic transit gloria mundi
It would have been so awesome! Perhaps too awesome for SW, like an intelligent Gamorrean who's part of the literari elite. In theory there could've been a Sith Emperor, but at some point the Council got rid of him and but decided that they could still utilise him as a construct. The 'Emperor' could provide both a god-like rallying symbol for the simple masses to cleave to and someone to distract lesser Sith and the Jedi.
And then the Jedi go on a wild goose chase to kill the 'evil emperor'!
And then the Jedi go on a wild goose chase to kill the 'evil emperor'!