Some additional thoughts......
They should have given Quentin a storyline of his own after Amanda is disposed of. Much of what Selby does here could have been done by anyone. A huge waste.
Perhaps Josette could have been the one to break through Barnabas' Leviathan programming. It would have awesome to have Josette's ghost appear to Angelique because she's the only one who can help Barnabas. There's Josette going to Angelique, knowing full well what she is and what she's done but needing her to fight a greater evil. Plus there's Angelique who should have mixed feelings of her own and not just about Josette. There's the conflict between her marriage vows versus her undying feelings for Barnabas. And there's the issue of her powers. It couldn't have been easy for her to give them up. It should be easy for her to get them back.
And, for once, break tradition and let the ingenue know what's going on. Carolyn may have been attracted to Jeb but she would have been horrified to let that he killed her father, let alone what he had planned for her and humanity. Like Maggie, Carolyn could have been a mole, relaying information to screw up their plans. And, at the right moment, Carolyn could have been the one to avenge her father's death, perhaps saying "Uncle Roger was right. You really are a cheap, insufferable pig."