The Best Case Scenario of NO DEAL?

If  the Yellowhammer document is the worst case scenario of a NO DEAL, what is the Government's best case scenario of a NO DEAL?   Surely, the Government must also publish the latter.  Both such documents are bound to be speculative.  The released document is totally negative, as is the BBC.  I would have thought that the best case solution is to leave the EU without a deal on 31 October, fulfilling the result of the referendum.  A deal could be negotiated, as other non EU countries do, after we have left.