I love the idea of Sidious dropping a reference to his new apprentice before there even is a Vader. That would be cool no matter how you handle the other stuff. He has it all mapped out. Then whether or not you actually admit Vader is Anakin in the end, it still gives a nice and subtle glimpse into how in control Palpatine actually is.

Not only cool, I think it would be important. Rather than some sort of flashback maybe someone could stumble upon his plans. That way Palpy is in control, all he needs is someone to encase in the Vader suit.

At the end of the day I'd be very happy if we see Luke born on Dagobah, and we DONT see Anakin literally burning.