Besides, there are ways to return the character to life without resurrectting him
Darth Vader, likes Boba Fett, is hard to separate from his armor.
It would be very Star Wars like to have a Dark Jedi use exactly the same armor as Darth Vader to terrorize the republic.
That's the original idea of the Dark Empire comic, then GL let the author brought Palpatine back.
But still I don't want to see some Vader imposter, we need a new villain.