Like I said, I could see it (although not Wanda so much). I just don't want it to be a Quicksilver movie, just an Inhumans movie.
But I do think they should strongly consider using Avengers as a launching pad for other franchises in the opposite of how the franchises launched the Avengers. Particularly, if, as I fear, the established movies are more or less going to be faded out.
A solo Black Widow movie would be a similar idea, although I understand the problems it poses (basically, there's going to be a lot of Romanoff character development in TWS and AoU, so the solo movie could feel like retreading the same ground. On the other hand, a legitimate spy movie could be fun.