I think it would be fascinating to showcase more force ghost “rules” and whatnot. I mean Luke appears to be the only one that sees them in ROTJ. Maybe depending on the soul of the individual, Luke sees Anakin as a Jedi from his prime, but maybe if Leia were to see his force ghost it would be the Sebastian version? Perhaps the whole conflicted force ghost Anakin thing was about exploring that idea, and maybe Kylo kept seeing that for idolizing Vader?

If force ghost Anakin were to return, and I think he should 100% along with Obi-Wan, I think it’d be interesting and satisfying to most people if we look into that aspect of force ghosts and hopefully see Hayden AND Sebastian’s Anakin.