I think that aizen has to break the hipnosis if he want to attack. All the times he has used his shikai in a battle, he appeard one moment before he attacks.That is probably the only open spot to defeat him and if i'm wrong it would be nearly impossible to kill him, once you have seen his shikai, he could just nulify all of his opponent's senses and kill him with ease. And I was wondering if his shikai is that powerfull, what is his bankai? shure, IF he has bankai.
what do you think about it, I'm right, or wrong?
ps:sorry about the englihs mistakes =p.