In fact, I came up with something extremely similar for healers about two years ago. There's many reasons not to do it. And I'd do it for healers before shamans, because quite frankly, shamans are pretty great as is. Yes, they could use a few tweaks to tie to their faiths more, you're right. It's something I'll think about, for all empowered classes. It is, however, a massive amount of work, and I'm not sure it's worth the ultimate reward.