Hal, have you considered having Luke speak to Ben during the Mustafar Opening or when he is repairing his mask? Maybe just a quick line like “Ben”, but something just to be consistent with Luke’s last words in TLJ of “see you around kid”.
I really, really like that! I think it works incredibly well! I also think that Luke shouting “Ben!” when he turns his head on Mustafar would be a good idea, but this is fantastic!