There MIGHT be another solution in case of such a tremendous amount of data; the "Cities in 3D" program by Google. They accept 3D data "en mass" from local governments, agencies etc. If you follow the big, green "Get started" button at the top left, you get to a page where you can communicate with Google and eventually (I suppose) send in 3D data other than orthogonally set skp/kmz files.