Assuming your models in question are polygonal geometry, isn't it possible to simply apply a shell modifier to all the objects at once? Shell should act the same as giving the objects "wall thickness", turning most non-manifold geo into "solids". If the models have open ends, then simply go into border mode, select all borders, and cap. Then select all, and apply a shell to all models at once. Not saying this will work in all cases, but it could work, depending on the structure of the models.
