Oh, I totally like Illyria. She has nifty resonance to all sorts of things, but I still don't think she really relates all that much to the original story S5 set out to tell. Her introduction was a kind of "bored now!" to the "are we selling out?" concept and a shift in another direction, in my mind anyway. It's still valid, but tonally different. (And since I'm writing a fic with Illyria in it, I can't say I'm not interested in those resonances; I was just amused to realize how little the two plots seemed to connect - perhaps that would have been rectificed by a hypothetical S6).