Since shapeshifting is fueled by magic and not by what race you are, it should be a class I suppose. Some races are a bit better at magic cause of their history in it or because they have a better connection to it but certain magical abilities aren't just easier for one race or another, it's magic in its entirety. If you can pull feats like shapeshifting physically, it should also be possible to pull other big feats with training for that kind of magic. Others aren't as lucky to be as good and can't do any of it. Correct me if I'm wrong Witch, you're still the one who made it up. Me being the one who fell asleep during you explaining it XD