My take on the types displayed so far:
Fighting as a standalone type itself is a good typing, and does make a lot of sense in terms of the transition from cub to aerial threat. A lot of Cartoons!' current backstory contains information regarding CAP1's quills hardening over time, allowing it flight. While it does indeed have quills, soft quills don't really allow any room for flight, since they do not produce the aerodynamic wind flows most birds ride and soar on. This makes the most sense flavor-wise if we want to go down the "cub to grown Pokemon" route.
If instead we wish to go the "untrained to trained" route, I'd recommend Flying / Normal. This places a huge emphasis in that it can fly, but has not mastered the arts of Fighting just yet. The Normal typing represents CAP1 in its most primal form as well.
Weak support to Flying / Fighting as there really isn't anything wrong with keeping CAP1's main typing. It is, however, a bit boring, and the given backstory (plus the creative willpower the CAP community possesses) really would allow more creativity for a different (yet similar) typing. This kind of is the ho-hum pick, where it's safe, but obvious.
Flying as a standalone type may seem tempting, but there are a few issues with this. One, there really isn't a huge flavor reason to make this pure Flying other than "Flying is CAP1's main type", which quite honestly really isn't a reason at all when you think about it. Yeah, you're right, but...what does that have to do with CAP1's story and background and development? I feel that it's a bit weak of an idea. Two, there currently is one true pure Flying type in the game (Arceus does NOT count, since Arceus' design and purpose does not give the connotation of "pure Flying" whatsoever since...that's not really what it is.): Tornadus. Tornadus doesn't have wings, though, and instead relies on a cloud to fly (much like the other genies). However, according to the current backstory, CAP1 does indeed have wings of some sort (fur that resembles feathers at the very least), but cannot gain flight until it stiffens the fur. It just cannot fly until evolved. So, this backstory (at least to me) doesn't add up to a Flying monotype pre-evo.
Normal / Fighting is pretty much the same as standalone Fighting, but with an added Fighting weakness and Ghost immunity (remember, movepools for CAP projects aren't necessarily type restricted fully). I don't think Normal is necessary to create a transformation to Flying after evolution, so it provides the same, if not less, flavor reasons as pure Fighting. Pure Fighting seems the superior choice.
Flying / Dark makes absolutely no sense to me. Nothing really suggests that CAP1 is a Dark type or should have Dark roots. While it looks like a "shaman" I suppose, a shaman himself isn't evil, but rather just practices rituals that he believes are good and beneficial. Not to mention that this technically is the pre-evo of said design, not even the shaman design. I don't see a flavor reason to have this at all (especially if the previous point is the only point supporting the Dark typing).
Flying / Steel makes even less sense. It's "cool" to use Eviolite for this Pokemon, but the only rationale I see is that Steel gives it more resistances for a defensive pre-evo. That's not a great reason, since aside from a competitive positive...there's not really any reason why a Steel typing makes sense here. Not sure how helmets = Steel, especially when helmets can be made of leather, feathers, and *gasp* fur. Steel makes 0 sense to this CAP.