Mmkay, that all makes sense and sounds fair.
My idea was for a twist on a Youkai, specifically a Kitsune (fox demon). Essentially he'd be rare (hence the need to ally himself with someone worth being allies with) but with his own strengths and able to work with the pack. He could either just show up at some point and try to gain trust or he could have established history with one or more of the pack so they know him. This is, of course, provided you're willing to accept another breed into the game.
Sounds good, though we'd need to figure out where he specifically falls in the "Demon/Shapeshifter" Paradigm. I realize in japanese Culture the word "Demon" doesn't mean quite what it does in Western culture. They use it a bit more liberally and it applies to many types of beings who might fall into other categories in western cultures.
In this setting most Demons(in the western sense of the word) have a particularly powerful hatred of Werewolves. So if you want a demon with fox-like traits that's fine but we'll need to hammer out some details on why he doesn't hate Werewolves like most demons do. On the other hand if he's just a "Werefox" that's fine too. I was pretty much already thinking that Werefoxes are sort of like Werecoyotes in that they're tricksters too, but a bit more focused than Coyotes.
Tricksters in general are usually looking to teach some sort of lesson with their tricks. They're big fans of irony. If you're a penny pincher and you attract a trickster's attention expect him to scam you for a fortune. Or clean out your bank account if you really raised that trickster's dander up. They're usually motivated toward some combination of teaching a lesson, getting a laugh, and turning a profit.
For example(borrowing this from some old RPG I read with tricksters)...a trickster might come to a wealthy person claiming to be an inventor in need of funding, and will present a genuinely good idea worth investing in. If the person just gives the trickster money without asking alot of questions the Trickster will pocket it and string them along indefinitely, milking as much more as possible from the hapless dupe before vanishing altogether. If the investor flatly refuses even though the proposal is good the Trickster might just move on...or he might decide that penny pinching bastard needs a lesson in giving others oppurtunities to succeed and wipe out the guy's bank accounts or burn down his business or something(preferably the punishment should fit the crime...but if all else fails, hacking Kiddy Porn onto his personal computer and anonymously tipping off the FBI works too...or Nair in his shampoo. Depends on how malicious the trickster in question is). However if the investor does their due diligence and invests moderately, while looking for regular progress updates and such(demonstrating good judgement, a willingness to help others, but not willing to be easily played for a fool) the Trickster will reward that person's wisdom by either delivering a genuinely good product or otherwise finding a way to bring some discreet good fortune their way.
Now in that scenario there's plenty of different ways a trickster can play things out. They can easily be malicious and set the scenario up so that their subject is all but certain to fail whatever kind of test the trickster is applying to them. Or the opposite if that they can set the person up to succeed. Or they can be plotting to pocket a profit for themselves all along, or be genuinely trying to teach a valuable lesson to somebody(maybe not even the target of the trick, but someone close to them). Or they could just be in it for a laugh from the very start. And hey, sometimes a laugh itself can be a lesson if you're teaching the prideful to come down off their high horse and stop taking themselves so seriously.
Generally speaking, Coyotes tend to go for the laugh. Foxes tend to go for the lesson. Ravens tend to be about pocketing a personal profit for themselves. That's not to say there aren't lesson-oriented Ravens and Coyotes, of Foxes who set their targets up to fail so they can pocket a profit for themselves. It varies from situation to situation and invididual to individual. But in broad terms, Coyotes want the laugh, Foxes want to teach, and Ravens just want shiny things to line their pockets/nests.