So, everything I've gotten by reading through is that the class is balanced, albeit underpowered.
Notes I've taken:
- Allow armor: Light armor mainly and allow fast movement to work in this.
- Natural Weapons: Maybe? I like the idea of choosing a type of natural attack instead of saying, "You get claws, deal with it." 2 claws, a bite, gore, tentacle, a tail or something else.
- More useful outside of wildshape: natural weapons and more weapon choices play into this.
As for knowledge checks to know creatures: the only rules for that I've seen is the awful "DC = HD" rule. Wouldn't be too hard to assign numbers to how common a creature is. Something like Common = 10, Uncommon = 20, Rare = 30, Unqiue = DC set by DM.
I'd say the DC would be set by the DM as they see fit, using current examples for guidelines.
As for the other factors- Usually classes without armor proficiency are ones that can effectively simulate it. Also, light armors are generally simple things that just about anyone can wear easily.
For Natural Weapons- Choose one from the list, change it as a standard action, maybe? Would fit the Shapechanger flavor. You also likely wouldn't need to worry about adding other weapon proficiencies.
If you'd prefer not adding light armor proficiency, possibly a defensive bonus like the offensive bonus options in the natural weapon ability.
You could also avoid excessive abuse of these low level abilities by saying that a player chooses one each of the weapon and defense at dawn. Just another thought.
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The problem with the shapeshift variant is that it doesn't apply well to other creature types, and generally the only stat that it increases is strength. There would have to be some way to apply it to a more expansive and versatile selection of creature types. Shapeshift is easy to apply to animals and elementals, since it's generic enough and there's not all that much variation between them. But things like Humanoids, aberrations, fey, etc. are hugely different between each creature.
I do enjoy the notion of having Shapechanging abilities from level 1, and keeping things balanced. I'm just not sure how it would work.
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Alternatively, half the supernatural special qualities most creatures seem to get include the special senses the class could obtain through an altered Manifest Senses class feature. *shrug*