User blog comment:Godisme/My Take on Isshin/@comment-1296831-20100329120456

One thing that doesn't make sense though, is the speculation that Ichigo's birth is significant because of his being a Shinigami-Human hybrid. If that was the "special power within", Aizen would have no reason to go to all of that trouble over him.

All he would have to do is go have a kid himself. Unless of course, he shoots blanks (XD). But really, there has to be something to it that hasn't been mentioned or speculated on so far...