Hmm...I'm glad that everyone likes the Favored Environment idea, and I'll work on incorporating that right away. As for weapon groups, Jag, I'd rather leave that to the Fighter, if you don't mind. I'm still looking out for that one fighter fix that fits into place here (with all the fixes out there, there's got to be at least one), but I'd like to keep the roles more or less the same.
Now, in regards to Favored Enemy being too restricting in this setting, I might have an idea. See, a bonus against everyone in the Fire Nation seems far too powerful to me, and a bonus against all animals seems nigh impossible in a setting where the Animal type includes things like mongoose dragons, kimodo rhinoceroses, and Shirshu. I'd say that if we made the categories narrower, the ability would serve the purpose it does in standard D&D. Something like this:
|Type (Subtype)||Type (Subtype)|
|Animal (mammal)||Earth Kingdom (military)|
|Animal (bird)||Earth Kingdom (Dai Li)|
|Animal (reptile)||Air Nomads (airbender)|
|Animal (aquatic)||Swamp (waterbender)|
|Magical Beast||Sun Warrior (firebender)|
|Vermin||Sun Warrior (warrior)|
|Fire Nation (firebender)||Monk (agile)|
|Fire Nation (military)||Monk (evasive)|
|Water Tribe (waterbender)||Monk (hard)|
|Water Tribe (military)||Monk (quick)|
|Earth Kingdom (earthbender)||Monk (resilient)|
This would make the ability considerably less powerful, and we'll have to define Fire Nation military, for example, as anyone trained to be part of the Firelord's armies and state that for any creature that falls into more than one category the ranger uses the highest modifier. What do you guys think?