User blog comment:CoolJazzman/Other Special War Powers?/@comment-6342763-20130428101124/@comment-6904925-20130428132317

Well actually Yhwach asked Aizen to be a part of his group own special war powers, that doesn't really state him as one of the 5 Special War power, but you might be right.

Plus Uryu I think Yhwach sees him with great potential and I think that he will ask him to join them as one of their own special war powers.