I saw the suggestion earlier in the thread, and with the Beast Mastermind in game, we have some samples of animals. If we got a few more, a Shapeshifting AT might be possible.
Primary Powersets for different animals; Bear, Wolf, Lion, Bird? or whatever.
Not sure what to use for Secondary powers though. Using the Druid example, nature powers, healing powers... With a witch as an example, go darker with darkness and pain?