Why isn't there any incentive to abstain from the werewolf/vampire traits? There should be a separate skill perk tree for characters who wish to pursue the teachings of Stendarr/Meridia. Such diversity would make for a richer gaming experience.

Perhaps we'll see something like that in the next ES game.

I think it's better to enhance the drawbacks of vampirism/lycanthropy than to balance them off with opposite equivalents. Let crusaders and witchhunters like the Dawnguard be the opposite. I don't the game should encourage everyone to get divine superpowers. That said, more distinctly Divine associated magic would be alright as well as more witchcraft. Skyrim has more of the latter than any previous game.