Personally, I would say that there should be a mixture of BOTH strategies. First, some greatly-needed triage would need to happen to, if nothing else, make the home inhabitable. Not perfect, but inhabitable. And while that is being done, the more in-depth plan should begin taking shape so that a long-term solution can be found and implemented as quickly as possible. If the either option were the ONLY option pursued, I would guess that the whole house would tumble down and need to be rebuilt entirely from the ground up.