I take it that either this isn't the cool idea I thought it was, or else it isn't one which a lot of people are interested in.
When I was devising my campaign world, I wanted to have "tribesmen" as a potential wandering encounter, as per good old 1st Edition. Because there are a lot of big lakes and rivers in the campaign starting area, I thought of these as semi-Native American, semi-Celtic tribesmen who used birchbark canoes, were generally pre-iron age, and had strong ties to the spirits in the area. Think woodlands rather than plains or pueblo culture.
I even devised rules for spirit quests, sacred bundles, and feats that required these things....The top end feats allow you to bind spirits to objects (swords, standing stones, etc.) or store spells in your sacred bundle to be released later. Fun stuff, good flavor for my world. So far these people -- the Lakashi -- are a hit....if only because they are less generic than most fantasy world humans.
Anyway, both the Celts and Native Americans had stories about animals taking human form. Obviously, the Native Americans exceeded the Celts on this theme, but my Lakashi are a lot more Native American than Celt. So, naturally, I thought of the OA hegeyokai. I renamed them faerie animals, made them fey (shapechanger), and voila!
Now the question of faerie animal types has come up. Could there be a faerie porcupine? A faerie stag? Overall, I think these would be cool additions to the game. My son has already started the thinking-it-through process (he wants to play the aforementioned faerie porcupine). The ECL of some animals would have to be more than the standard for hengeyokai, though, and I don't have much practice yet at assigning ECLs.
(If anyone is interested, I am also using the OA Shaman as a base core class in the setting, and some of the prestige classes are in use as well. There are some other neat concepts that I think would port well to a standard game, but I haven't found the time to do it yet....I am building this world as I go.)
Daniel