Speaking of Anakin reborn, another interesting theory I heard was that Snoke is actually Anakin's divided dark side spirit. When Darth Vader died on the Death Star, he became Anakin again as a force ghost as seen at the end of ROTJ, right? Well, what if his dark side was able to manipulate the immortality that comes with being a Jedi founded by Qui-Gon to become his own being?
So, technically, the force ghost from ROTJ is Anakin, and Vader is Snoke.
That's the next best thing after Snoke being Plagueis.