If by standard space vehicle requirements you mean the materials requirements and workmanship specs, these are covered in (endless) documents. The NASA and ESA web-sites are a good place to start. In terms of modular design, many companies do try to work with a basic design which is tried and...
I also use COSMOS FE analysis software, and higly recommend it for ease of use. I'm currently looking at CAD import from a variety of CAD packages. I currently use Rhino and have to use the IGES import, but solidworks, ProEng, and a number of other packages are supported directly. Contact Mark...