The reason for the large size of Evetaku's AKB0048 BD, is because there are some other good stuffs bundled in there. If you only want the episode, try using uTorrent so you can choose what file in the torrent you want to get. Anyway, the whole bunch of files there is worth getting in my opinion.
I was thinking also they'd be two center novas, with the creation of another AKB team, the understudies. Nagisa or Chieri go to the "old" team to be center nova and the others will be led by the remaining nova.