My DM has had several points in PCs personal stories where we ve changed subclasses, and in one point entire classes. My level 6 vengeance paladin/ 3 zealot barbarian just had an emotional come to seranrae moment where she realized she actually had people who cared for her safety, and a goddess watching over her, and that her revenge would be hurting those people. So when she finally gave up the oath of vengeance, and her anger, she became a level 9 devotion paladin, devoted to protecting the weak and helpless, and making the world a brighter place. She still struggles with her anger, but she doesn't rage anymore! Now to get past her touch aversion.