The file format exists, its Compound Document Files which are effectively just a little FAT filesystem in a file from memory. both Microsoft and 3rd parties (..

The file format exists, its Compound Document Files which are effectively just a little FAT filesystem in a file from memory. both Microsoft and 3rd parties (...Autodesk maybe?) use them. My favourite example of seeing them is VBA macro projects in office documents. The macros used to be stored in CDFs equivalent of a subfolder within a wider Word CDF document. When Office 2007 migrated from .doc to .docx, they just made the VBA project folder its own CDF file and stuck it in the new zip archive format