I always thought that he sent just them to free Ichigo, because he knew that Ichigo was really the only way that he would be able to win the war against Aizen. xD And I thought he sent some of his strongest shimigami, but not all of them, because I swear some of them weren't Captains.
I think that Orihimi wasn't the same because she had to fuse the Hougyoku with Aizen didn't she? So may she lost her powers. I can imagine her being the fall of Aizen to Ichigo, or at least a reason for Bleach not to finish, as she might be able to restore Ichigo's powers or something if Aizen doesn't die. But I can't imagine that happening. =\