Well if you use functools like you started with in your lead up examples your talking about what two lines of boilerplate (functools decorator and function definition)? Personally I often times just add the four lines of boiler plate and forgo functools.... Look I'm not saying that your library is a bad idea; Its neat, in fact it seems to handle a few thing better than the more well known decorator library does.
( Out of curiosity though how about the functions signature, I think functools doesn't maintain the original functions signature but I think decorator does, what does funcy do? )
For me personally I feel its better to have the decorator all in one place where you can see everything that is going on, and making it a class makes it pretty straight forward to understand.