I'm not going to lie and said that I've meticulously analyzed this gargantuan thread, but I have read quite a bit of the most popular suggestions, and I have one great concern:

Adywan has openly voiced his desire to keep the reveal of Vader as a surprise. This is logical, as the twist in ESB is essentially negated by the prequel trilogy, and would be much more enjoyable if it was kept as the amazing twist it was intended to be.

This preservation however, raises some problems that no one has proposed viable solutions to. How do you have the prequel trilogy, in which the ENTIRE PLOT centers around Anakin's inevitable downfall, stand without it's core motivation? And how would you even make it even slightly ambiguous without butchering the ending?

To keep Anakin's transformation secret, you must:

A.) Make the audience believe that this Vader is a new character without seeming out of place

B.) Explain how Anakin becomes Vader without it being blatant, but also holding up to logic

C.) Make it seem like these two are not one and the same, and

D.) Make it appear as though Vader has killed Anakin.

I have yet to read a single viable way of making any of those elements work. This is a major flaw, several major flaws actually. Enough flaws to make me question as to whether keeping the secret would be worth it or not.