BEOS requires a separate blockchain so we can modify it to interface with BitShares as necessary without requiring changes to BitShares or EOS. It also needs to be able to implement jurisdictional agility which required special signing nodes. Finally, this method allows us to restrict tokens to users of BEOS who are willing to move their tokens there. It's a way to eliminate those who don't like or trust us from getting control of voting shares. We give them only to true believers.