Alright! So! I have Gabby for either Beatris or Irina! My plan with him is for him to get much darker. He's been lost since Max left and his long-time on-off girlfriend up and disappeared. His drinking has gotten worse and he really only needs a push to get into the deep end.
So my ideas are either we have him turn Beatris, and if she demands he help her, it could be further proof to him that the world is out to get him, etc. But he'd definitely stick around to help.
OR
Irina. Let's say during her first full moon, her wolfy self runs into Gabby's wolfy self and sort of follows along. Then when they're in their human forms, she asks him for help dealing with being a werewolf. He'd probably refuse but we could arrange a series of run-ins in which she wears him down.
And perhaps Charlotte and Ducky? Ducky certainly won't pretend to hate magic, but he's a likable guy, and was very popular during his schooling, so she probably knows him. He's working as the Caretaker at Hogwarts so they could easily have reason to interact. He'd probably constantly try to get her to lighten up.