The Saab factory would not be suitable for producing the Tesla model 'S'. The Saab factory is set up for building Saab vehicles and everything - from the BIW assembly process onwards would need to be replaced for production of a car like the model 'S'.
If Saab does go bankrupt, the likelihood is that a Chinese manufacturer will buy the production equipment and lift and shift it to China. At that point you have an empty building, and they're everywhere.
There is plenty of production facilities across Europe that would be suitable for Tesla model 'S' production. The Matra or Pininfarina facilities woud make a much better match for Tesla.