Well, so redemption is certainly possible for a human being that renounced the coin.
And maybe some holder might be the dominant partner (or at least the clever one) and use the demon for the greater good. Or so he thinks. But do the ends justify the means?

A demon seeking redemption doesnīt really seem appropiate in the Dresdenverse, but if it works for you, go ahead. Or maybe the demon just doesnīt want to destroy the earth and the human race - that might be a very strange bedfellow in fighting world-ending or humanity-destroying fiends.

"Just another teenage girl" could work. Or "Virgin Girl" (if she is). "Sacrifice-to-be" or "Potential Sacrifice" or even "Not your typical helpless sacrifice".

No... not really.

I just had a player who wanted to play a were-something, so he flipped through an animal book... and came up with a were-herring. Or a were-dustmite. 

Good question... the rules arenīt very clear on this.

Now, in the side commentary relating to the power, Billy says that "itīs a bit of an evil people eater" power", which suggests to me, that those powers you mimic are actually gone from your "donors"; even though only the entry on supernatural powers makes a clear statement on this. That would mean - even though a handshake might do the trick - your opponent would probably notice that something was off.

Or, you could make up your own stunt, which wouldnīt steal power, but only copy mortals stunts and skills, maybe with one mimic point for free and just the touch requirement.