Shapeshifting in pathfinder
Although I could go on for pages in a polymorph-based argument, I would like to avoid that for this thread. Instead, I was wondering if someone could help me. I'm wanting to create a shapeshifter, preferably as a sorcerer or bard. However, I can't find any shapeshifting abilities in pathfinder that are anything more that Bull's Strength with natural armor tacked on.
Thematically, I find shapeshifting attractive because it creates a character who is seemingly weak and defenseless, and who is completely reliant on the shapeshifting in order to defend himself. Is there anything like this in pathfinder?