Repair what they can in-situ, then add enough strengthening inside and outside to make it airworthy (but ugly). Fly it empty and depressurised to Boeing or somewhere that can do the job properly in a controlled environment. This will probably involve the replacement of a large section of the fuselage with a new construct.
Huh? I haven't paid much attention to this thread - small battery fire, no big deal - so it comes as a surprise that the hull might need strengthening for a ferry flight back to the factory. Can't be true, given the assurances that the composite structure survives fire better than aluminum, etc.