These kinds of questions usually belong to the main DFRPG forum, this is a collection. I'm sure Sanctaphrax will move it over in a bit.
Until then, lets see.
Mimic Form would be a higher powered fetch thing, I think. Glamours to conceal their identity is a first step, probably. Crossing over in mirrors seems like something I would do as part of an aspect. "You're part fetch, so you can cross over into the nevernever in places that make sense. Like using mirrors as a gate. It's difficult enough to find big enough mirrors, anyway. If you want to give him more substance for that, worldwalking would be the obvious choice. Maybe for -1 instead of -2 and limit it to mirrors only.
Incite Emotion(Fear) is another obvious one, I would say. Probably even the first one. You could even attach some powers to a hunger(fear), if you are so inclined.
Claws could work, but might look weird on a changeling. Any of the inhuman powers should work as well.