The problem though is that some people might have given Raphael the crown and the power boost that comes with it. There's going to be a significant difference between writing a plot for a cambion that's been empowered like unto a god and one who's licking his wounds. Again, Zariel is really a non-issue since her stuff only connects to Karlach and Gortash, one of whom is definitely dead and the other of whom is possibly dead. Hope also could be dead or left imprisoned too for that matter. There's just not a lot reliably left over from the game to justfy an Avernus DLC.
