Raven/Mystique will definitely be a more unlikely ally as she actively making movements against the Magistrates (there was something very boldly audacious and telling that happened between Raven and then at the Ball and Lucifer should appreciate).

Also she could be the one who could give him the swift kick to accept that the wings don't define him, he defines his wings. Being to understand that she is beyond making shallow moral judgement about other but seems to see them for who they are. When CR is higher future reveal of true face, nature, why she has more resistance to his devilish ways, and share their similar pasts. (Really want to hear Lucifer sing.)

Show she's not an Usurper or a threat in the way of Chloe but is in fact a good and trusthworthy partner and hopefully a friend who could be relied on.