A timeskip? That would definitely throw my idea out of the window. I thought that it would be a flashback first, and then a timeskip (which would make more sense, seeing what happened while it still strongly relates to Aizen, the Vaizards, and Isshin) kind of like what Naruto did, with the Kakashi Gaiden during the timeskip itself.
And wasn't it mentioned that one arc would be longer than the other? Again, it would make more sense if the shorter one was the flashback, and the longer one was the timeskip.