This should come as a surprise to no one, but when Adam and I should be working on the tough bits like editing, we often get sidetracked to instead messing around with some potential new classes. We actually got half way through writing a Barbarian a few months back.
ANYWAY, the Druid's been something we've messed around with too. A few of the thoughts that we've had (also by way of John Harper):
-The fictional change is by far the most important bit. You play a druid so you can say "I turn into a bear!" not so you can say "I've got +1 STR! Oh, and I guess I look like a bear?"
-Shapeshifting needs to be the core of the druid, so it should be a meaty, interesting move. Spellcasting might not even really be part of the druid. Maybe something like the bard, where they can pick up the Cleric's spellcasting later.
-Moves that make you say more about the thing you turn into are good. A really good move will draw out what you actually mean when you say "I become a hawk!" Cause when I hear that I think you're probably fast and dangerous to small mammals, but you might think that you've also got great sight.
-Mechanically limiting the things you can become is tricky. The druid's all about being the right creature at the right time, but there's also some limitations on it. If you can only be an eagle, bear, or lion at first level that might work for some people but not for others.
I think this move scores big on the generality, but it doesn't help draw out detail on the new shape much, and it may not be interesting enough to hinge a class on. That's fine if the druid also casts spells, of course.
Here's an idea that just came to me while writing this post:
Wild Shape
When you take on the form of a wild beast, roll+Wis. Your new form has some useful adaptations. On a 7-9 name two useful adaptations, on a 10+ name three. Your new form also has some basic animal instinct, the GM will name it.
Adaptations
When your form's adaptations make you well-suited for a situation, take +1 to any applicable roll.
Instinct
When you give in to your animal instinct your connection to your form strengthens. Take -1 forward to Wild Shape, but the next time your adaptations apply you get +2 instead of +1.
And some advanced moves that might tie to it:
Flexible Shape
When you Wild Shape on a hit you may choose to name only one adaptation and hold your remaining choices for later as you fine-tune your shape.
True Form
You can take on the form of not just wild beasts but elementals and plants as well. You also get one more adaptation on a hit.
Civilized
You can also take on the form of specific humanoid creatures, impersonating them perfectly. Of course this only affects your physical form, not your personality, mannerisms, clothing or equipment.
The only thing I don't like about this is the arbitrary number of adaptations. Might get rid of that somehow, but then I don't know how to differentiate strong and weak hits. Hmm.
Anyway, that's my thoughts on shapeshifting. Hope they help!