I love the concept and what the storyline could bring from that, and how great they would work together, but I don't think it could work. Technically, since Fynch is still living, he can still resurrect his light-bearing knight. And you know how our ghosts couldn't revive Cayde? Fynch is bound to his guardian now and forever. He couldn't revive Eris if he wanted to. And since Eris has already lost her original ghost, it's pretty much game over for her. Other wise, the vanguard and anyone else in or near that position would have dragged a ghost over Cayde's dead body and had the ghost revive him. But that's not what happened was it? Like I said, I love the concept but it wouldn't happen.. And what about Eris's iconic ahamkara bone that got her through the hive's magic and deep caves? It wouldn't be so monumental if she had a ghost, or specifically, Fynch.