To be frank, the thing that bothers me most about Nethys is how Paizo seems to think being bipolar balances each other out so that in the end you'll be Neutral. But that's not what it's like at all. As somebody who knows a bipolar person (he plays in our group) having "sudden, unpredictable mood swings" is pretty much the opposite of being stable enough to do what Nethys is expected to do.

All in all, Nethy's "madness" just feels too contrary to his actual motives and actions.