I'll be honest with you guys.
I'm glad they cut the whole ghost Luna as a party member thing.
I was really against the idea and felt it took away from the integrity of the story, since one of my favorite themes in it is that only Death brought Noctis and Lua finally together. I felt heavy interaction between them, even in ghost form, would take away from that a lot.
Her appearance her was brief but strong, and more in line with the themes and atmosphere of the story. It was a moment pf divine intervention that brought Noct hope and determination, but he still, couldn't tell Luna what ge wanted to say.
So I really hope the party member thing is actually cut content and we'll never see it again. Now, the Regalia? That's another matter.