I would love to see someone do an index doujin story revolving around Yuriko and Touma, whether she's already reformed (prior to later arcs) or not. it'd be awesome either way, to see how a female accelerator would go about slaughtering the clones, or how she joins GROUP only to detract and do something berserk-like.
go ahead, look me in the eye and tell that wouldn't be an awesome spin-off