I am and have always been against Plagueis ever being seen as it takes away from the mystique and ambiguity of The Tragedy of Darth Plagueis the Wise.

However, the idea of the Knights of Ren being the reanimated corpses of Sith intrigues me. I think they should be at least mostly those we’ve seen onscreen. Imagine, at the end of the trilogy, seeing them unmask themselves and they’re the rotting corpses of Darths Bane (although technically mentioned, he was created by Lucas, and was the invetor of the Rule of Two, so important enough to warrant a spot), Plagueis (yeah, I’m circumventing my rule, but hey, he’s a corpse here, so it’s fine), Maul, Tyrannus, and last but not least Vader, with Ventress to round out the cast (not technically a Sith but like Kylo is essentially the same thing).

Palpatine should still be on top.