I know this is probably a sacrilegious thing to say, but I think Hayden as Anakin’s force ghost actually makes more sense. It might sound dumb right now but let me explain.
Vader/Anakin was 46 when he died. Hayden is currently 39 and doesn’t look much different then he did in ROTS. I’m pretty sure he’s not going to suddenly look 78 in 7 years.
So even if we take into account the fact that he was good again when he died so ROTS wasn’t the last time he was on the light side of the force, it STILL makes more sense for Hayden to be the ghost.
Hayden being in the movie assumes you’ve seen the prequels, which Adywan is not assuming.